4. Electricity and magnetism Flashcards

Question

What is the direction of an electric field at a point?

Answer 1

The direction of the force on a positive charge at that point

Answer 2

A region in which an electric charge experiences a force

Answer 3

1. Charged object is held close to the conductor 2. Electrons in the conductor are able to move towards or away from the object

Answer 4

A material that allows charge to flow through it

Answer 5

A material that does not allow charge to flow through it

Answer 6

Metals and graphite

Answer 7

Non-metals and plastics

Answer 8

A negatively charged particle

Answer 9

Rate of flow of charge

Answer 10

I = Q ÷ t

Answer 11

Flow of electrons

Answer 12

Amperes (A)

Answer 13

Always in series

Answer 14

Positive to negative

Answer 15

Energy supplied by a source in driving 1C of charge round a complete circuit

Answer 16

Amount of energy transferred by each unit of charge passing between those two points

Answer 17

In parallel with the part of the circuit you want to measure the potential difference of

Answer 18

Opposition to current

Answer 19

R = V ÷ I

Answer 20

Set the power supply to a low voltage (1 or 2 V) Use a voltmeter and ammeter to obtain voltage and current readings Substitute readings into the equation R = V ÷ I

Answer 21

Length is proportional to resistance

Answer 22

Cross-sectional area of a wire is inversely proportional to resistance

Answer 23

Battery/power source → circuit components → surroundings

Answer 24

E = Pt / E = VIt

Answer 25

The same at every point

Answer 26

The sum on individual resistances

Answer 27

Total p.d. across the supply

Answer 28

Current from the source is larger than the current in each branch

Answer 29

Current from the source is larger than the current in each branch

Answer 30

Less than that of either resistor by itself

Answer 31

Currents in separate branches

Answer 32

Lamps can be individually controlled, using their own switches If one lamp stops to function the other will continue to work Each lamp gets maximum p.d.

Answer 33

Potentiometer

Answer 34

Potentiometer

Answer 35

The resistor with a largest resistance will have greater p.d. than the other

Answer 36

A coil of wire with a sliding contact along it

Answer 37

1. Increases or decreases the length of wire 2. Increases or decreases resistance (and hence p.d.)

Answer 38

A resistor that changes its resistance when it is heated

Answer 39

Temperature is inversely proportional to resistance

Answer 40

A resistor that changes its resistance when light shines upon it

Answer 41

Light is inversely proportional to resistance

Answer 42

V.out = V.in × (R2 ÷ R.Total)

Answer 43

Takes in physical energy and converts it into an electrical signal that can be read

Answer 44

A coil and magnetic switch

Answer 45

When there is a current in the coil it creates a magnetic effect This attracts the switch, closing it This can be used to control a switch in a separate circuit

Answer 46

A component which only allows charge to flow in one direction through it

Answer 47

Positive to negative

Answer 48

Rectification

Answer 49

Conversion of a.c. to d.c.

Answer 50

When it gets darker, resistance increases This causes an increase in p.d. Increase in p.d. causes an increase in current in the coil A large enough current in the coil will attract the switch, closing it This allows a current to pass through

Answer 51

Temperature-controlled (temperature-operated alarm) circuits work the same way as LDR-controlled circuits

Answer 52

Analogue and digital

Answer 53

One that is continuously varying and can take any value

Answer 54

One that can only take one of two (discrete) states

Answer 55

An electronic component that gives a particular output, depending on the input(s) to it

Answer 56

Electric shock

Answer 57

Electrocution

Answer 58

Protects a circuit

Answer 59

If the current in the wire becomes too large The wire heats up and melts The wire breaks, stopping the current and breaking the circuit

Answer 60

The fuse should always have a higher current rating than that needed by the appliance - without being too high

Answer 61

An automatic switch which Current rises over a specified value Electromagnet pulls the contacts apart Breaking the circuit

Answer 62

Earth wire provides a low resistance path to the earth This causes a surge of current in the earth wire and also in the live wire High current in the fuse causes it to melt and break This cuts off the supply of electricity to the appliance

Answer 63

When the conductor is moved across the magnetic field, it cuts through the field lines This induces an e.m.f. in the conductor

Answer 64

Opposes the change that produces it

Answer 65

If a wire is passes across a magnetic field/changing magnetic field A small e.m.f. is induced in the wire This can be detected by a galvanometer

Answer 66

Moving the wire faster Using a stronger magnet Adding more turns to the coil

Answer 67

One that continuously changes its direction

Answer 68

One that is steady and only flows in one direction

Answer 69

One that is steady and only flows in one direction

Answer 70

One that is steady and only flows in one direction

Answer 71

Mains electricity

Answer 72

Electric cells (batteries)

Answer 73

As the coil rotates, it cuts through field lines This induces an e.m.f. and hence a current The size of the e.m.f. could be increased by: (List) Slip rings transfer current to the metal brushes whilst allowing the coil to rotate freely

Answer 74

The ends of the coil

Answer 75

When the coil is horizontal

Answer 76

The coil cuts through magnetic field lines at the fastest rate

Answer 77

Remember to say ‘add more turns to the coil’ and not ‘add more coils’ – if you give the second one it will be marked wrong.

Answer 78

An electrical device that can be used to increase or decrease the voltage of an a.c.

Answer 79

Direct current

Answer 80

Increases the voltage of a power source

Answer 81

Decreases the voltage of a power source

Answer 82

A.c. is supplied to the primary coil A changing magnetic field is produced by the coil The field passes through the soft iron core and secondary coil Changing field in the secondary coil induces an e.m.f.

Answer 83

High-voltage transmission of electricity

Answer 84

1. Reduces power loss 2. Thinner, cheaper cables can be used

Answer 85

Current causes heating in wires Resulting in power loss Increasing voltage reduces current Smaller current causes less heating in wires Less power is lost

Answer 86

A magnetic field around the wire

Answer 87

Concentric circles around the wire

Answer 88

Direction and magnitude of current

Answer 89

The strength and direction of the field depend on the size and direction of the current: - If the current is increased, the field will get stronger - If the direction of the current is changed, the direction of the field will change The strength of the magnetic field is related to the distance between the field lines: As the field lines spread out, the field gets weaker The field lines around a wire get further apart the further they are from the wire

Answer 90

The direction of the force on the N pole of a magnet at that point

Answer 91

Direction of force reverses

Answer 92

Direction of force reverses

Answer 93

1. Moving charges forms a current 2. The field exerts a force on the particle, deflecting it

Answer 94

1. Using a cathode ray tube and a pair of magnets 2. Passing a collimated beam of beta particles between the poles of a horseshoe magnet

Answer 95

Increasing the number of turns on the coil Increasing the current Increasing the strength of the magnetic field

Answer 96

Current passes through the coil Current creates a magnetic field around the coil This interacts with the field of the magnets Force is exerted on the coil This pushes one side of the coil up and the other down Creating a turning effect The split-ring commutator reverses the direction of current in the current every half turn

Answer 97

To reverse the direction of force and keep the coil spinning

Answer 98

iron steel nickel cobalt

Answer 99

Same poles repel Opposite poles attract

Answer 100

1. Magnetic field is strongest when field lines are closer together 2. The direction of the magnetic field shows which direction a compass would point 3. Magnetic field lines point away from north and towards south 4. Field lines never cross

Answer 101

constant magnetic field - constant direction + strength arrows point in same direction, field lines are equally spaced apart, magnetic field strength = constant can be made in the space between opposite poles of a magnet

Answer 102

permanent magnets are made of magnetically hard materials eg steel, which retain their magnetism once magnetised temporary magnets eg electromagnets are magnetically soft eg iron, which lose their magnetism once they are no longer exposed to a magnetic field and are easy to magnetise and de-magnetise

Answer 103

Indicate the size and direction of the magnetic force

Answer 104

Place a bar magnet on the centre of a piece of paper Bring a plotting compass close to end of North Pole of magnet but stop it touching magnet Mark where the compass needle is pointing next to compass Lift up plotting compass and place the centre of it on the mark made on the paper Repeat until the South Pole is reached, join up dots Repeat for at least another 5 lines, starting each line near the North Pole but at a different place

Answer 105

Place a sheet of paper on a horizontal surface and place two bar magnets North Pole to South Pole next to each other Leave a gap between them at least four times width of plotting compass Bring plotting compass close to end of North Pole and draw a small dot next to where arrowhead is pointing Move and repeat Repeat for at least another four lines from the North Pole

Answer 106

Magnetism is induced

Answer 107

movement of electrons around atom therefore a wire carrying a current (conductor) produces a magnetic field around it

Answer 108

movement of electrons around atom therefore a wire carrying a current (conductor) produces a magnetic field around it

Answer 109

soft iron core wrapped in a coil of wire when current flows through coil of wire it becomes magnetic

Answer 110

more turns in coil iron core increase current

Answer 111

reversing the current reverses the poles of the electromagnet

Answer 112

iron is magnetically soft/ gains/loses magnetism easily

Answer 113

Relay = switch controlled by electromagnet Electromagnet with small current passing through it closes switch by pushing an armature into the contacts Closing the switch using an electromagnet reduces chance of electric shock

Answer 114

Current passes through electromagnet Magnetic field around electromagnet not strong enough to attract contact If there is a surge in current strength of magnetic field increases and electromagnet attracts contact Breaks circuit

Answer 115

Alternating current is passed through electromagnet Changes polarity of electromagnet Electromagnet attracts and then repels permanent magnet Causes magnet and cone to vibrate creating a soundwave pitch = change frequency of alternate current which change frequency of vibration loudness = increase current in electromagnet, stronger magnetic field around it, larger force of attraction and repulsion between it and fixed magnet -> increased amplitude of vibration

Answer 116

1.button pressed 2. Current flows 3. Electromagnet operates 4. Attracts armature 5. Strikes gong 6. Circuit broken at screw 7. Electromagnet turns off

Answer 117

Current that flows from + to - battery terminals

Answer 118

force on charged particle (eg in a wire carrying an electric current) when it moves in a magnetic field as long as its motion is not parallel to the field this is because magnetic field produced by moving charges interacts w/ magnetic field of permanent magnet

Answer 119

Increasing size of magnetic field Increasing size of current Making angle between conventional current and magnetic field closer to 90’’ (if current (conducting wire) was moving parallel to field then there would be no force) Use longer wire

Answer 120

alpha deflected in opposite direction (have opposite charge) gamma not deflected beta is deflected the other way to alpha

Answer 121

When a current flows in the coil a force is applied to it Current in each side of the loop is in opposite directions Force on one side is upwards and on other side it is downwards One side of the loop will be forced to the top, the other to the bottom (rotate clockwise) The coil will then oscillate and eventually line up vertically with one side at the top and one at the bottom

Answer 122

increase current increase number of turns in coil increase strength of magnetic field increase length of wire

Answer 123

Current flows in a coil of wire Creates a magnetic field around coil of wire Interacts with field from permanent magnet Causes force on loop of wire which causes it to start rotating Split ring commutator changes direction of current every half turn as it spins, reversing direction of current and reversing direction of force so it can keep spinning

Answer 124

Directs current through magnetic field

Answer 125

Prevents wires getting tangled allowing coil of wire to rotate

Answer 126

changes direction of current every half turn changes direction of force, allowing it to rotate for more than half a turn

Answer 127

conductor/wire cuts through magnetic field lines potential difference is induced if wire is part of complete circuit a current will flow wire and magnetic field must move perpendicular to each other (no field lines are cut if move parallel to each other, no potential difference is therefore induced)

Answer 128

More turns in coil Stronger magnetic field Faster movement

Answer 129

Changing direction of magnetic field Changing direction of movement

Answer 130

Device that electrically transfers kinetic store of generator into other stores (opposite of electric motor) Produce electricity

Answer 131

coil of wire is spun in magnetic field coil cuts through magnetic field lines so potential difference is induced as coil spins each part of wire sometimes movs up and sometimes down because it changes direction current that is induced is an alternating current (changes direction)

Answer 132

split ring commutator converts alternating current into direct current

Answer 133

spins magnet in a coil as wheels move instead of coil of wire magnetic field lines cut through sides of coil inducing potential difference in coil magnetic field constantly changing direction as it rotates, output current is also alternating - so unlike normals dynamos it produces a ac not dc current

Answer 134

connect coil to brushes, maintains a/c inside coil to a/c in outer circuit

Answer 135

silver, copper, alumininum, steel (delocalised electrons)

Answer 136

rubber, plastic, glass, wood but can conduct a bit of static electricity, just not a flow of charge

Answer 137

initially neutral force of friction causes electrons to move

Answer 138

cloth: more protons -> positive rod: more electrons -> negative

Answer 139

electrons are repelled by other electrons, and these are attracted to protons

Answer 140

yes! electrons are not within nucleus

Answer 141

rod approaches paper, electrons in paper are repelled away from rod makes one side of paper negative and other positive positive side is closer to rod resultant force = attractive as opposite charges are closer paper sticks to rod works the same if rod is positive -> electrons attracted to one side

Answer 142

electrons flow onto (if object positively charged) or off of object (if negatively charged, as the elctrons repel each other and move away from each other)

Answer 143

charge on object is neutralised by transfer of electrons

Answer 144

they are repelled

Answer 145

they are attracted

Answer 146

to print copies of an image/document

Answer 147

image of document is projected on to positively charged drum drum loses charge in light areas and keeps positive charge in dark areas (light areas conduct electricity) negatively charged toner sticks to where there is a positive charge on drum transferred onto paper

Answer 148

ink droplets positively charged via charging electrodes pass between oppositely charged plates computer controls plate voltage droplets attracted towards negatively charged plate + repelled from positive one (the deflection can be changed by altering strength of plate charges) direction changed by changing the charge of the plates

Answer 149

paint droplets given charge by paint sprayer so repel each other-> fine mist and covers large area oppositely charge car less waste, more even coverage

Answer 150

reduces pollution dust becomes charged by passing thru negatively charged plates dust removed from air as attracted to positively charged plates dust removed from collecting plates as it is neutralised upon touching the plates, falls into dust collection

Answer 151

droplets + ice crystals rub against each other in cloud during storm, creates static electrical charge clouds have positive and negative side negative side is at the bottom -> when there is enough charge in the cloud it is released via lightning bolt, which is goes to anything oppositely charged (eg lightning conductor, positively charged, earths it)

Answer 152

build up of static charge : friction between fuel and pipe, fuel gains charge -> could spark and fuel could ignite and explode (also friction with air whilst flying can cause a charge) explosion prevented by fuel tank being connected to earth w conductor carriers charge through to earth to reduce sparking risk

Answer 153

Rate of flow of charge

Answer 154

current = charge(c)/time(s) I=q/T

Answer 155

(voltage) energy gained or lost by each electron (energy transferred per unit charge)

Answer 156

potential difference = energy transferred (J) /charge (C) v= e/q

Answer 157

measure current

Answer 158

measures voltage should be paralell to component

Answer 159

what determines/reduces flow of current

Answer 160

increases (electrons gain more energy, move faster)

Answer 161

potential difference = current x resistance

Answer 162

divide by 1000 there are 1000 milliamps in one amp

Answer 163

material length thickness temperature

Answer 164

length of wire is increased, electrons have to travel further chance of collisions increases causes resistance to increase

Answer 165

increasing thickness of wire increases area that electrons can flow through decreases chance of collisions w metal ions causes resistance to decrease

Answer 166

ions vibrate faster harder for electrons to flow temp increases -> resistance increases

Answer 167

current is directly proportional to poterntial difference if temp is constant thus component that obeys ohms law has constant resistance (the gradient)

Answer 168

current increases -> more FREQUENT collisions of electrons w ions rate of energy transer to ions increases ions vibrate faster resistance of wire increases

Answer 169

whether a current is flowing

Answer 170

reduce the current in a circuit have some resistance energy is transferred

Answer 171

reduce the current in a circuit have some resistance energy is transferred

Answer 172

resistor has fixed resistance bulb has a changing resistance bulb emits light

Answer 173

emit light resistance isn’t constant energy transferred

Answer 174

current can only flow in one direction bulb -> current can flow in either direction

Answer 175

sense diff temps and switch off an oven when it gets too hot

Answer 176

as it gets hotter -> more electrons get excited + become available for conduction resistance drops

Answer 177

sense light levels and switch on streetlamps when it gets dark

Answer 178

as it gets brighter, more electrons get excited and become available for conduction -> R drops

Answer 179

each electron transfers more energy to the bulbs

Answer 180

more electrons pass through bulb each second

Answer 181

electric current

Answer 182

energy transferred= current x voltage x time E=IVT (energy in joules)

Answer 183

P=IV power in watts

Answer 184

P=IV power in watts

Answer 185

power = energy/time

Answer 186

there is only one path

Answer 187

take different paths around the circuit

Answer 188

so they can be switched on and off independently

Answer 189

the other bulbs will still work whereas in a series they would all go out

Answer 190

current is the same throughout circuit potential difference is shared between components (bulbs will get dimmer the more you add) total resistance = adding resistances of individ components

Answer 191

potential difference is same throughout circuit current splits at each junction (more current flows through the branch with smaller resistor) use v=ir to calculate current

Answer 192

increases current resistance of circuit decreases

Answer 193

electrons continually change direction mains electricity is ac

Answer 194

dc (direct, electrons flow in same direction)

Answer 195

cells have chemical stores which are transferred electrically, mains depends constant low voltage, alternating high voltage DC, AC 50Hz is typical freq for UK mains

Answer 196

conductor, flexible

Answer 197

insulator, flexible

Answer 198

conductor, rigid

Answer 199

insulator, rigid

Answer 200

brown high voltage carries current that alternates between neg and pos volatge

Answer 201

green safety wire used to earth appliances w a metal case

Answer 202

blue completes circuit kept at 0 voltage

Answer 203

surge in current could damage an electrical appliance fuse contains thin wire -> melts if current too hgh this breaks cirucit and elecrticity unable to flow fuse rating gives current for which the fuse will melt eg 3A fuse should be slightly larger than normal operating current

Answer 204

reduces chance of shock earth wire connected to casing of metal device to provide alternative path for current if fault occues if live wire becomes loose and touches metal case, v large current flows (low resistance) to eath and melts the fuse wire breaking circuit

Answer 205

plastic casess case cannot become live, doesn’t conduct if one layer of insulation damaged the appliance is still safe

Answer 206

circuit broken by using an electromagnet to pull two wires apart

Answer 207

use alternating magnetic fields to induce currents in saucepan, which heats saucepan little energy transferred to thermal store of surroundings, making it v efficient

Answer 208

Alternating current in primary coil produces continually changing magnetic field within iron core Iron core guides magnetic field into secondary coil Field lines continually moving because magnetic field is changing strength Potential difference is induced across secondary coil because secondary coil cuts through field lines If secondary coil is attached to a circuit then current will flow

Answer 209

transforming alternating voltage from a larger/smaller value to a smaller/larger value

Answer 210

more turns in secondary coil increases voltage decreases current no effect on output power (because P=IV)

Answer 211

fewer turns in secondary coil decreases voltage increases current power stays same

Answer 212

Because power = current x voltage, current decreases

Answer 213

Vp/Vs = Np/Ns P= primary S= secondary N= number of turns

Answer 214

input power (IpVp) = output power (IsVs)

Answer 215

Power in secondary/power in primary x 100

Answer 216

Power in secondary/power in primary x 100

Answer 217

In direct current, magnetic field would be constant so no field lines would be cut and there would be no potential difference generated

Answer 218

Heat is produced in coils, since current is flowing through them Magnetic field in core produces current which also causes heating Magnetic field may leak out of core if there is an air gap between primary and secondary

Answer 219

heating in wires -> use low resistance wires eddy currents in iron core -> laminate iron core leaking magnetic field -> use an iron core to direct current through coils of wire

Answer 220

used to increase voltage of electricity supply after it has left power station -> lower current, less heating of wires, less energy wasted voltage reduced at sub stations before reachers consumer, as this is safer

Answer 221

A charged atom

Answer 222

Transfers electrons to the surface atoms of rod from the cloth, so the rod becomes negatively charged. Electrons gained in the polythene rod. Atoms in dry cloth becomes positive as a result of losing electrons.

Answer 223

Transfers electrons from the surface atoms of the rod to the cloth, so the rod becomes positively charged. Atoms become positive in the perspex rod as a result of losing electrons. Electrons gained by dry cloth.

Answer 224

Battery. A cell is necessary to push electrons around a complete circuit. A battery consists of two or more cells.

Answer 225

Switch. A switch enables the current in a circuit to be switched on or off.

Answer 226

Indicator. An indicator is designed to emit light as a signal when a current passes through it or as a light source such as a bulb.

Answer 227

Ammeter. Used to measure current.

Answer 228

Resistor. Limits the current in a circuit.

Answer 229

Variable Resistor. allows the current to be varied.

Answer 230

Voltmeter. Used to measure voltage.

Answer 231

Diode allows current through in one direction only.

Answer 232

LED Emits light when a current passes through it.

Answer 233

Fuse designed to melt and break the circuit if the current through it is greater than a certain amount.

Answer 234

Heater. Designed to transfer electrical energy to heat the surroundings.

Answer 235

… is the rate of flow of an electric charge.

Answer 236

Coulombs (C)

Answer 237

Charge flow (C) / Time taken (s)

Answer 238

Energy transferred (J) / Charge (C)

Answer 239

Electrons having to push past lots of vibrating ions in a metal filament.

Answer 240

Voltage / Current

Answer 241

The current through a resistor at constant temperature is directly proportional to the voltage across the resistor.

Answer 242

Filament Bulb Diode

Answer 243

Thermistor A resistor that depends on temperature.

Answer 244

Light Dependent Resistor A resistor that depends on the intensity of light.

Answer 245

The same amount.

Answer 246

It is shared between all of the components.

Answer 247

It is split up, and runs through separate components.

Answer 248

Electric current in a circuit that is in one direction only.

Answer 249

Electric current in a circuit that repeatedly reverses its direction.

Answer 250

The mains wire that has a voltage that alternates between +325 and -325v (in Europe)

Answer 251

The wire of a mains circuit that is earthed at the local substation so its potential is close to zero.

Answer 252

The use of a diode in a circuit with an alternating supply pd to allow current in only one direction every other half cycle of the supply pd.

Answer 253

A mains socket is used to connect the mains plug of a mains appliance to the mains circuit.

Answer 254

Brass (Its a good conductor, and it doesn’t rust or oxidise)

Answer 255

The earth plug, because it is the first pin that connects with the wall socket, so the plug is earthed even before the other pins connect.

Answer 256

A fuse contains a thin wire that melts and cuts the current off if too much current passes through it.

Answer 257

The appliance and the wires of a circuit.

Answer 258

An electromagnetic switch that opens and cuts the current off off if too much current passes through it.

Answer 259

They work faster They can be reset

Answer 260

An RCCB cuts off the current in the live wire when it is different from the current in the neutral wire. More sensitive than fuses/ normal circuit breakers.

Answer 261

…series.

Answer 262

Current (A) x Voltage (V)

Answer 263

energy is transferred to the resistor, so the resistor becomes hotter.

Answer 264

(kwh) Electrical energy supplied to a 1kW device in 1 hour.

Answer 265

A unit of energy

Answer 266

More, because they give the same amount of light energy for the same input of electrical energy.

Answer 267

very inefficient heat from the bulb makes the plastic casing go brittle and crack.

Answer 268

More efficient that filament bulbs

Answer 269

Use a low voltage and low power V. Efficient Last much longer.

Answer 270

raise voltage lower current

Answer 271

Lower voltage Raise current

Answer 272

Bend away from the midpoint.

Answer 273

The field between the poles is uniform.

Answer 274

The magnetic field lines are parallel to each other.

Answer 275

Iron (Easily magnetised and demagnetised)

Answer 276

ferrous metals

Answer 277

> Scrapyard cranes > Circuit breakers > Electric bells > Relays

Answer 278

A coil of insulated wire

Answer 279

Increasing the current Using a stronger magnet

Answer 280

When the wire is perpendicular to the magnetic field.

Answer 281

Circles centred on the wire in a plane perpendicular to the wire.

Answer 282

Circles centred on the wire in a plane perpendicular to the wire.

Answer 283

…reverses the magnetic field lines

Answer 284

When a CURRENT is passed along a wire in a magnetic field, A FORCE IS EXERTED on the wire by the magnetic field.

Answer 285

When the wire is parallel to the magnetic field.

Answer 286

Movement Field (N to S) Current

Answer 287

Split Ring- Reverse the current on every half turn to keep the motor spinning constantly.

Answer 288

Slip-ring - Doesn't alternate the current because it alternates already.

Answer 289

The process of inducing a potential difference/voltage in a wire by moving the wire so it cuts across the lines of force of a magnetic field.

Answer 290

The production of voltage using a changing magnetic field.

Answer 291

The Voltage’s Polarity

Answer 292

A coil that spins in a uniform magnetic field.

Answer 293

When the coil is perpendicular to the magnetic field lines.

Answer 294

When the coild is parallel to the direction of the magnetic field.

Answer 295

Direction of coil tells us which pole it corresponds to. North- iN sOUTh- OUT

Answer 296

No current when the wire is stationary A current is generated when the magnet moves but not the wire. Faster movement = More current Current reverses when the direction of motion reverses.

Answer 297

A changing magnetic field.

Answer 298

Vicky needs 5 A’s Voltage Can Make Vicky Cry PC Ian Can’t Solve Crime A A A A A V C M V C PC IC SC

Answer 299

An alternating voltage in the primary coil creates an alternating current there. This creates an alternating magnetic field in the iron core This induces an alternating voltage in the secondary coil, which induces an alternating current.

Answer 300

An alternating voltage in the primary coil creates an alternating current there. This creates an alternating magnetic field in the iron core This induces an alternating voltage in the secondary coil, which induces an alternating current.

Answer 301

Has more turns on the secondary coil, so increases voltage.

Answer 302

Has less turns on the secondary coil, so decreases voltage.

Answer 303

… the better the efficiency of the transformer.

Answer 304

Vp / Ip = Vs / Is V = Voltage I = Current

Answer 305

Vp / Vs = (No. of turns) Np / Ns

Answer 306

…The greater the frequency of the AC current + The larger the peak value of the AC current.

Answer 307

A transformer that works between 50 000 Hz and 200 000 Hz

Answer 308

> Lighter and Smaller > Higher frequency

Answer 309

If the voltage was lower more curren would be needed for the same amount of power to be transferred. The cables would overheat and result in more wasted energy.

Answer 310

North to South

Answer 311

Current flowing in one direction

Answer 312

Changes direction

Answer 313

It is a controlled resistor and it is used as volume control and as potentiometer- controls the current.

Answer 314

Allows current to flow in one way only

Answer 315

The straight line should be on the side of the negative - terminal of the battery

Answer 316

Change ac to dc by rectification

Answer 317

Is a low resistance path for the current to follow

Answer 318

Safety precautions to prevent electric shock

Answer 319

Damaged insulation Overheating of cables Damp conditions since water is a conductor

Answer 320

A device for converting a non-electrical input into an electrical signal

Answer 321

Detects changes in the environment and converts them to electrical signal

Answer 322

Thermistor LDR Thermocouple

Answer 323

LED’s Heater Bell Loudspeaker

Answer 324

Handled information which is represented by continuous change and flow, such as voltage and current

Answer 325

Represent data in discrete units

Answer 326

0 1 1 1 0 1 1 1 1 0 0 0

Answer 327

0 0 0 0 1 0 1 0 0 1 1 1

Answer 328

0 0 1 1 0 1 0 1 1 1 1 0

Answer 329

0 0 1 1 0 0 0 1 0 1 1 0

Answer 330

Iron Steel Nickel Cobalt

Answer 331

Iron Steel

Answer 332

Hard to magnetize- long time to magnetize Permanent magnet

Answer 333

Easy to magnetise- short time to magnetize Temporary magnet

Answer 334

Because of the existence of tiny magnets inside. When a magnetic is brought near it, its tiny magnets are arranged uniformly

Answer 335

By induction By stroking By electrically

Answer 336

Place magnetic material in a solenoid connected to dc current

Answer 337

Hammering a magnet Heating Dropping a magnet Demagnetising by using reduced AC through a coil of wire wrapped round a magnet

Answer 338

The area around a permanent magnet or a wire carrying a current.

Answer 339

Concentric circles

Answer 340

Circuit breaker Magnetic relay

Answer 341

Control high voltage system with low voltage or control high current system with low current

Answer 342

The low voltage circuit is on so there is a current in the solenoid. The magnetic field in the solenoid attracts the armature and the current flows through the contacts so the high voltage is on.

Answer 343

A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit.

Answer 344

Increasing current Stronger magnet Increasing length of wire in the field

Answer 345

Coil of wire Two magnets Split ring commutator Brushes

Answer 346

The current flows in opposite directions on each side of the armature which will create two opposite forces act as different line making the armature only spin half a cycle The split-ring reverses the current direction through an armature every half turn so the armature will continue to spin in the same direction

Answer 347

Increasing current Increasing number of turns Increasing area of the coil Using a stronger magnet

Answer 348

The turning effect will be maximum

Answer 349

It decreases

Answer 350

The EMF induced in a conductor is proportional to the rate at which magnetic field lines are cut by the conductor

Answer 351

Moving wire faster Stronger magnet Increasing the length of wire inside the magnetic field

Answer 352

A very sensitive ammeter

Answer 353

An induced current always flows in the direction such opposes the change which produced it

Answer 354

Magnet at a faster speed Stronger magnet More turns of wire on the coil

Answer 355

Mechanical work into electrical work

Answer 356

The wire cuts the m.f lines inducing an emf that causes induced current in the coils. If the wire is moved in the opposite direction the induced current also moves in the opposite direction This means that as a coil is rotated in magnetic field, the induced current reverses direction every half turn. This is called alternating current.

Answer 357

Increase number of turns Use a stronger magnet Increase the area of the coil Rotating the coil faster

Answer 358

Step up transformer Step down transformer

Answer 359

Two coil and one on each side of a soft iron core

Answer 360

AC current passes through the primary core which creates a changing magnetic field in the iron core. The changing magnetic field then induces alternating current in the secondary coil. The induced emf depends on the number of coils in the secondary coils.

Answer 361

Voltage A/ Voltage B= Number of turns in A/ Number of turns in B

Answer 362

Using direct current will create a mf in the core but it will not be a changing mf and so no voltage will be induced in the second coil

Answer 363

V1 * I1= V2 * I2

Answer 364

Minimise energy loss as current decreases therefore it is less expensive

Answer 365

A magnetic field

Answer 366

The stronger the magnetic field

Answer 367

The direction of the current

Answer 368

A field made of of concentric circles with the wire in the centre

Answer 369

Around the centre of the flat circular coil of wire it is similar to that of a bar magnet Around the coil there are concentric ellipses (stretched circles)

Answer 370

Strong and uniform inside current carrying solenoid - Outside the coil it is like a bar magnet (ends of solenoid act as a north and south pole making an electromagnet)

Answer 371

Hard or soft

Answer 372

It looses its induced magnetism quickly (temporary magnet)

Answer 373

It looses its induced magnetism quickly (temporary magnet)

Answer 374

The magnetism is kept permanently (permeant magnet)

Answer 375

Because of its properties - it needs to magnetise and demagnetise 50 times per second

Answer 376

Add soft iron core

Answer 377

Turn on and off Change the magnetic field strength Change the shape of the magnet

Answer 378

Lifting metal objects and the electric bell

Answer 379

Current carrying wire wrapped into coil, wrapped around an iron core

Answer 380

The creation of a voltage in a wire which is experiencing a change in magnetic field

Answer 381

Transforming kinetic energy into electrical energy (in a power station this kinetic energy is provided by turbines)

Answer 382

When an electrical conductor moves through a magnetic field (cutting the magnetic field lines) causing the electrical conductor changes

Answer 383

By connecting an ammeter to a conductor and moving the conductor through a magnetic field - it will show the magnitude and direction of the induced current

Answer 384

The induced voltage/current will be reversed too

Answer 385

The strength of the magnet The number of turns on a coil The speed of the movement

Answer 386

Motor - you have a current in the wire and magnetic field which causes movement Generator - You have a magnetic field and movement which induces a current

Answer 387

They rotate a coil in a magnetic field which produces a current

Answer 388

A current is induced in the coil. The current changes direction every half turn

Answer 389

An ac voltage - the faster the revolutions produce more peaks and higher overall voltage

Answer 390

They produce electricity - they get the energy needed to turn the coils or magnetic field in different ways

Answer 391

As the magnet falls through the coil, there is a changing magnetic field acting on the coil. This inducers a voltage across the coil and a current through it

Answer 392

The magnet will be moving faster so the induced voltage will be greater

Answer 393

(i) Reading decreases - less voltage (ii) Reading increases - more voltage (iii) Reading will be negative

Answer 394

1) The magnetic field is being cut forcing the amplitude to decrease as the spring with the magnet attached, slows down gradually 2) It goes from positive to negative

Answer 395

Direction of magnet changes Amount of field lines cut changes Speed of magnet changes (Any one of these answers)

Answer 396

When you put a current carrying wire in a magnetic field (causes the wire to move)

Answer 397

It is because charged particles moving through a magnetic field will experience a force as long as they’re not moving parallel to the field lines

Answer 398

90 degrees to the magnetic field (wont work if the wire runs along the magnetic field)

Answer 399

The same direction relative to the magnetic field of the magnets and the direction of the current in the wire (north-south poles)

Answer 400

The direction of the magnetic field - Direction of the current

Answer 401

Apply a current to a set of rails inside a horseshoe magnet. A bar is placed on the rails which completes the circuit - this generates a force that rolls the bar along the rails

Answer 402

The strength of the magnetic field

Answer 403

The amount of current flowing through the conductor

Answer 404

It also reverse the direction of the magnetic field

Answer 405

Which way the force acts

Answer 406

Thumb - Motion (force) First finger - Field Second finger - Current

Answer 407

Using your left hand point your first finger in the direction of the field and your second finger in the direction of the current. Your thumb will then point in the direction of the force (motion)

Answer 408

The magnetic field due to the current in the foil interacts with the permanent magnetic field of magnet, causing a force on the foil so, the foil moves.

Answer 409

Magnetic fields

Answer 410

Two poles (north and south) - The poles are the strongest part of a magnet

Answer 411

A region where magnetic materials (iron) experience a force

Answer 412

The size and the direction of the magnetic fields - always point from north to south

Answer 413

It creates a uniform field between the two magnets (straight lines going from north to south)

Answer 414

Compasses and ion fillings

Answer 415

Align themselves with the magnetic field

Answer 416

Put a magnet(s) under a piece of paper and scatter the iron fillings on top

Answer 417

Use more than one compass/ a compass and move it around a magnet (trace the pathway on a piece of paper)

Answer 418

Any magnetic materials or other magnets

Answer 419

That material acts as a magnet (the magnetism has been induced by the original magnet)

Answer 420

The stronger the induced magnetism will be

Answer 421

Little induced magnetism

Answer 422

Magnetism induced

Answer 423

More current More turns on the coil Stronger magnetic field A soft iron core in the coil

Answer 424

Using a coil of wire that is free to rotate between two opposite magnetic poles. When an electric current flows through the coil, the coil experiences a force and moves (interaction)

Answer 425

A force is acting on the two side arms of the coil. Because the coil is on a spindle (one side acts up and the other down) it rotates (it is the forces between the two magnetic fields that cause the coil to turn, transferring electrical energy to kinetic energy)

Answer 426

Split- ring commutator - clever why of swapping the contacts every half turn to keep the motor rotating in the same direction

Answer 427

Swap the polarity of the dc supply - Swap the magnetic poles over

Answer 428

Flemings left hand rule

Answer 429

Loudspeakers

Answer 430

AC electrical signals from an amplifier are fed to a coil of wire in the speaker which is wrapped around the base of the cone

Answer 431

A permanent magnet - the ac signals cause a force on the coil and make it move back and forth

Answer 432

The cones vibrate which creates sounds

Answer 433

Change the size of the voltage of an alternating current

Answer 434

Two coils, the primary and the secondary, joined with an iron core

Answer 435

The magnetically soft (iron) core magnetises and demagnetises quickly. This induces an alternating voltage in the secondary coil

Answer 436

The ratio between the number of turns on the primary and secondary coils

Answer 437

They step the voltage up - they have more turns on the secondary coil than the primary coil

Answer 438

They step the voltage down - they have more turns on the primary coil than the secondary

Answer 439

The input voltage and the number of turns on each coil

Answer 440

Input (primary) voltage /Output (secondary) voltage = Number of turns on primary/ number of turns on secondary

Answer 441

Vp/Vs = Np/Ns or both equations flipped around

Answer 442

Power in = power out

Answer 443

Power = voltage x current or P= V x I

Answer 444

VpIp = VsIs Vp = Primary voltage Ip = Primary current Vs = Secondary voltage Is = Secondary current

Answer 445

Transmitting mains electricity

Answer 446

Used when transmitting electricity across the country

Answer 447

It is too low - the lower the voltage the higher the current for a given amount of power, causing the wire to heat up

Answer 448

To boost the voltage before it is transmitted

Answer 449

Used at the end of the journey to reduce the voltage so its more useful and safer to use

Answer 450

Charge = current * time Q = I * t Q = C (coulombs) I = A (current) t = S (seconds)

Answer 451

Attracted by a magnet and can be magnetised Iron Nickel Steel Cobalt Steel = Permanent Iron = Temporary

Answer 452

Not attracted by magnet and can’t be magnetised Copper Silver Aluminium Wood Glass

Answer 453

Amount of force exerted by the charge on a unit charge (Q) placed at a point in the field E = F / Q

Answer 454

Voltage across resistor is directly proportional to current R = V / I R (measured in Ohms)

Answer 455

V = Energy / Charge V = E / Q

Answer 456

EMF = lost volts inside the power source + terminal p.d EMF = Ir + IR

Answer 457

R = resentivity * (Length of a resistor / Area of cross section of the resistor) R = resentivity * (L / A)

Answer 458

Series = Stays the same - Parallel = Current divides

Answer 459

Series = Divides - Parallel = Stays the same

Answer 460

R = R1 + R2 + R3 The R’s are all resistances of resistors in Ohms

Answer 461

1 / R = 1 / R1 + 1 / R2 + 1 / R3

Answer 462

V1 / V2 = R1 / R2

Answer 463

V2 = (R2 / (R1 + R2)) * V

Answer 464

P = V * I P = I^2 * R P = V^2 / R P = Energy / time

Answer 465

Semiconductor device Current pass only in one direction, rectifier

Answer 466

Semiconductor device works as a switch, collector, base, emitter

Answer 467

LED is dependent on light Brightness increase = resistance decrease

Answer 468

Dependent on temperature Temp increase = resistance decrease

Answer 469

Parallel conductor with insulator in between to store changes

Answer 470

Electromagnetic switching device

Answer 471

Thumb = Motion First finger (index) = Field Second finger = Current

Answer 472

Np / Ns = Vp / Vs

Answer 473

Vp / Vs = Ip / Is Vp * Ip = Vs * Is

Answer 474

EMF or current is induced in a conductor when it cuts the magnetic field lines

Answer 475

Produces current Fleming’s RIGHT hand rule

Answer 476

Consumes current Fleming’s LEFT hand rule

Answer 477

AND (both input needs to be 1 for output to be 1) OR (output will be 1 if one or both inputs is 1) NOT (opposite of the input) NAND (output is 1 when input = either 1/0 0/1 0/0) NOR (output will be 1 when input = 0/0)

Answer 478

Stream of electrons emitted from heated metal (cathode) Process is called thermionic emission

Answer 479

Horizontal or y-plates for vertical movement of electron beam Timebase for x-plates for horizontal movement

Answer 480

Use iron filings and a sheet of plastic. Place the magnet under the plastic. Sprinkle iron filings over. Tap gently to evenly distribute. The filings will show the field lines.

Answer 481

from North to South

Answer 482

Place compass at end of magnet.Mark position of the end of compass. Move end of compass needle to new mark and repeat

Answer 483

The magnetic field is stronger where lines are closer together

Answer 484

Use two permanent bar magnets. Place the south of one magnet opposite the north of the other magnet Place them at the correct distance apart to get evenly spaced lines.

Answer 485

magnetic field

Answer 486

The field around a straight wire forms concentric circles

Answer 487

It changes direction/ reverses

Answer 488

The field produced round a single flat coil or loop of wire looks like:

Answer 489

The conductor (wire) moves

Answer 490

If a current carrying wire is placed in a magnetic field it experiences a force and moves.

Answer 491

At right angles/ perpendicular

Answer 492

Thrust, movement, force.The direction the wire will move if placed in a magneti field.

Answer 493

Field - magnetic field. From North to South.

Answer 494

A turning force is produced if the wire is made into a coil. This effect is used in simple DC (direct current) electric motors.

Answer 495

fans electric drills food processors washing machines CD and DVD players

Answer 496

When a current carrying coil is placed in a magnetic field it will rotate the current flowing through the coil creates a magnetic field the field around the current interacts with the field produced by the magnet the forces combine to make the coil rotate

Answer 497

increase the size of the magnetic field increase the size of the current increase the number of turns on the coil

Answer 498

Is used in an electric motor to change the direction of current every half turn to keep the coil rotating.

Answer 499

When a magnet is moved into a conductor (such as a coil of wire) a current will be induced.

Answer 500

increase the strength of the magnetic field increase the speed of rotation of the magnet increase the number of coils add iron core inside coil

Answer 501

A material that is attracted by a magnet. Can become magnetised when placed in a magnetic field.

Answer 502

A material that stays magnetic after it has been magnetised.

Answer 503

A permanent magnet

Answer 504

A material that does not stay magnetic once it has been magnetized.

Answer 505

Used in electromagnets - as they can be switched on and off

Answer 506

take a bar of iron (of the hard magnetic type) and stroke it repeatedly in the same direction with a magnet.This will induce a magnetic field in the magnet.

Answer 507

place the iron bar inside a coil of wire carrying a current.Again this will induce a field in the bar.

Answer 508

The magnet induces magnetism in the nail and it becomes magnetised.

Answer 509

Power = Current x VoltageorP = IV Where I – current in amps (A) V – voltage in volts (V)

Answer 510

P = IVP = 230 x 0.08= 18.4 W (this would probably be an energy-saving bulb)

Answer 511

P = IVI = P/VI = 2000/230I = 8.7A

Answer 512

P = IVV = P/IV = 2.5/0.5V = 5V

Answer 513

P = IVI = P/VI = 1000/230I = 4.35A

Answer 514

P = IVP = 12 x 0.5P = 6 W

Answer 515

P = IVP = 230 x 0.2P = 46 W

Answer 516

E = IVtWhereI – current in amps (A)V – voltage in volts (V)t – time of flow in seconds (s)E – energy used in joules (J)Notice that: P = IVSo we can replace the It in the equation above with: E = Pt

Answer 517

Frayed Cables Long cables Damaged Plugs Water Metal Objects

Answer 518

The Earth wire

Answer 519

Double Insulated

Answer 520

DC Direct Current

Answer 521

AC alternating Current

Answer 522

Light-dependent Resistor LDR LDRs, change their resistance according to the amount of light that falls on them. As a result they can be used to monitor light levels. Say you want a light to come on automatically when it gets dark.

Answer 523

Thermistor Thermistors change their resistance according to the temperature around them. These devices can be used to respond to temperatures, for instance, if you want a cooling fan to come on when a device gets too hot.

Answer 524

An LED Light-emitting Diode These are devices that produce light when a current is passed through them. Think of your computer. You might have an LED for the power being on.

Answer 525

As we add more components into a circuit the resistance of the circuit increases. This has the effect of reducing the current that flows. Essentially: more resistance →→→→→→→→→→→ less current

Answer 526

An Ameter.

Answer 527

As voltage increases the current increases.

Answer 528

Current = charge transferred/time taken or I = Q/t Where Q – charge measure in coulombs (C) I – current measured in amps (A) t – time measured in seconds (s)

Answer 529

I = Q/t I = 60/150 (we have changed the minutes into seconds) I = 0.4A

Answer 530

I = Q/t Q = It Q = 0.2 x 60 x 60 (Note that one hour is 60 minutes of 60 seconds each: 60 x 60 = 3600 s) Q = 0.2 x 3600 = 720 C

Answer 531

I = Q/t I = 200/30 x 60 I = 200/1800 I = 0.111A

Answer 532

I = Q/t Q = It Q = 4 x 6 x 60 x 60 Q = 86400 C

Answer 533

We can use a formula known as Ohm’s law to relate current voltage and resistance in circuits. R = V/I This is usually written as: V = IR V – voltage in volts (V) I – current in amps (A)

Answer 534

R = V/I R = 12/0.2 R = 60 Ω

Answer 535

R = V/I I = V/R I = 230/3000 I = 0.077A

Answer 536

V = IR V = 0.5 x 200 = 100 V

Answer 537

R = V/I I = V/R I = 40/650 I = 0.062A

Answer 538

joule/coulomb

Answer 539

Current flow in metals is a flow of electrons which have a negative charge.

Answer 540

current is a flow of charge

Answer 541

When a LDR is illuminated its resistance decreases. A circuit component designed to change its resistance as its temperature changes is know as a thermistor. One component designed to produce light when current passes through it is a light emitting diode. This is usually abbreviated to the letters LED.

Answer 542

V = JC-1 volt = joule per coulomb

Answer 543

Rub two insulators together

Answer 544

Negatively charged

Answer 545

It has lost electrons

Answer 546

Risk of a spark causing an explosion (e.g. lorries containing fuel) - reduce risk by ensuring that lorry is earthed Risk of a getting a shock - use insultation, such as wear insulating shoes or use an insulating mat.

Answer 547

Dust attracted to computer or tv screen - use anti-static spray or cloth. Materials clinging to skin - use anti-static cleaner

Answer 548

No, because the electrons in metal can flow easily so if electrons were transferred onto the metal rod they would flow away rather than staying on surface of object and making the metal charged.

Answer 549

2 from: Spray Painting Smoke Precipitators Defibrillators

Answer 550

Method: Suspend the two rods. Rub both rods with a cloth.If they carry the same charge they will be repelled .If they carry different charge they will be attracted.

Answer 551

Try to pick up small peices of paper with it Use it to deflect a stream of water. Try to deflect gold leaf

Answer 552

before rubbing both are neutral electrons move from the cloth to the rod plastic rod gains electrons becomes negatively charged cloth looses electrons becomes positively charged

Answer 553

Yes, some materials will become positively charged, some will become negatively charged.

Answer 554

It has gained electrons

Answer 555

Conductor (best)

Answer 556

Conductor (moderate)

Answer 557

conductor (poor)

Answer 558

semi-conductor conductor (moderate)

Answer 559

insulator (best)

Answer 560

conductor (poor)

Answer 561

conductors

Answer 562

insulator (but living tree conductor as contains water)

Answer 563

1. Fewer wires 2. Lower resistance

Answer 564

1. One element fails - the circuit fails 2. No independent control

Answer 565

1. a failure of one component does not lead to the failure of the other components 2. more components may be added in parallel without the need for more voltage

Answer 566

1. power remains at the same voltage as the voltage of a single power source 2. Lower resistance 3. split of an energy source across the entire circuit

Answer 567

open switch

Answer 568

LDR Light-dependent resistor

Answer 569

A lamp or bulb

Answer 570

A fixed resistor

Answer 571

An ammeter

Answer 572

A variable resistor

Answer 573

A fuse (melts or blows when the current is too big)

Answer 574

LED Light Emitting Diode

Answer 575

thermistor

Answer 576

variable resistor

Answer 577

a magnetic field

Answer 578

Pass a current through it

Answer 579

Steel - retains its magnetism once magnetised

Answer 580

Iron - loses its magnetism easily and is therefore a useful temporary magnet

Answer 581

leave it in a magnetic field

Answer 582

The volume of space around a magnet where magnetism can be detected

Answer 583

Using iron fillings or compasses which will align with the direction of the magnetic field

Answer 584

Their magnetic fields affect each other

Answer 585

A phenomenon where a magnetic field is created around a wire that has current passing through it

Answer 586

increase the current in the wire wrap the wire into a coil or a solenoid (a long coil)

Answer 587

Its poles are also reversed

Answer 588

increase the current flowing through increase the number of turns of the solenoid wrap the solenoid around a magnetically soft core such as iron

Answer 589

the combination of soft iron core and solenoid

Answer 590

Bell push pressed; circuit complete and current flows Soft core of electromagnet is magnetised and attracts the iron armature Armature moves so hammer strikes bell Gap created at contact screw Circuit incomplete and current stops flowing Electromagnet turned off so spring’s armature returns to original position

Answer 591

If current is too high the electromagnet is strong enough to pull the iron catch out of position so that the contacts open Circuit breaks But can be reset with reset button

Answer 592

In circuits with a large current there is a danger of receiving a large electric shock. A relay switch uses a small current in one circuit to turn on a second that may have a much large current

Answer 593

Switch of small circuit closed so current flows As current passes through coil C the iron core is magnetised and attracts the iron armature The armature is pivoted so its lower end pushes the contacts of the second circuit together Now the second circuit is complete and current flows.

Answer 594

If switch S is opened the electromagnet is turned off Iron armature moves back to its original position and contacts spring apart Circuit off b/c current can no longer flow

Answer 595

It experiences a force

Answer 596

If its motion is not parallel to the field

Answer 597

Pass a current through a wire held at right angles to the mag.field of a magnet.

Answer 598

The two magnetic field lines interact around the wire and the magnet. In certain places, the fields are in the same direction and so reinforce each other giving a strong magnetic field. Where the fields are in opposite directions weaker fields are produced. The wire experiences a force pushing it from the strong to the weak field. MOTOR EFFECT

Answer 599

stronger mag.field increased current

Answer 600

The wire experiences a force in the opposite direction

Answer 601

Signals from amplifier fed into coil as a.c The coil now has a changing magnetic field that interact with those of the magnet creating varying forces on the wires of the coil. This makes the speaker cone vibrate The vibrations create the sounds waves we hear

Answer 602

Lets the connections to the supply through the brushed swap over so current continues to flow in the same direction and the motor turns consistently

Answer 603

Changes the direction of the current every half turn which means that the rotation can be continuous

Answer 604

increase the number of turn of wire COIL increase the strength of mag.field increase the current flowing

Answer 605

Curved electromagnets which are capable of producing strong mag.fields

Answer 606

Single loop is replaced with several coils of wire wrapped on the same axis; makes the motor powerful allows it to run more smoothly

Answer 607

Coils are wrapped on a laminated soft iron core to make motor more efficient and powerful

Answer 608

Motors use electricity to produce movement….generators movement to produce electricity

Answer 609

By large generators in power statioms

Answer 610

When a wire is moved across a magnetic field at right angles, a voltage is induced in the wire.

Answer 611

If the wire is part of a complete circuit

Answer 612

move the wire more quickly use a stronger magnet wrap the wire into a coil (move wires move in the mag.field)

Answer 613

a voltage can be generated by pushing a magnet into a coil

Answer 614

move the magnet more quickly use a stronger magnet using a coil with more turns using a coil with a large cross sectional area

Answer 615

the rate at which the magnetic lines of flux are being cut

Answer 616

The size induced voltage is dir.prop to the rate at which the flux lines are cut

Answer 617

it too, reverses

Answer 618

As the cyclist pedals the wheel rotates and a magnet in the dynamo spins around. As it turns its field lines cut through the surrounding coil inducing a current in it This current is used to work the cyclist’s lights

Answer 619

Uses: STRONGER MAGNETS MORE COILS OF WIRE SPINS COIL FASTER

Answer 620

ALTERNATING CURRENT IS PRODUCED

Answer 621

ALTERNATOR

Answer 622

AC current passed through coil Its magnetic field is changing; as current increases field grows and visa versa If a second coil placed near first, changing mag.field of first coil interacts with the second’s coil inducing and a.c. current Size and direction of current induced changes depending on current provided to first coil

Answer 623

TRANSFORMER

Answer 624

input V/output V = turns on primary coil/turns on secondary coil

Answer 625

p1 = p2 v1 x I1 = v2 x I2

Answer 626

energy is lost in the form of heat

Answer 627

The wires on pylons are long and have a high resistance

Answer 628

By transporting at low I and high V

Answer 629

Step-up transformer to increase V and decrease I

Answer 630

High voltages in the cables is v.dangerous

Answer 631

STEP DOWN TRANSFORMER - increase current

Answer 632

via underground cables

Answer 633

it can magnetise and demagnetise 50 times/second because it is magnetically soft

Answer 634

90 degrees

Answer 635

conventional current (+ to -)

Answer 636

from positive to negative

Answer 637

creation of a voltage (maybe current) in a wire experiencing a change in mag.field

Answer 638

Using electromagnetic induction to transfer kinetic energy to electrical energy

Answer 639

Attach an ammeter to it; when moving it through the magnetic field the ammeter will shows the magnitude and direction of the induced current

Answer 640

Higher overall voltage and more peaks (higher frequency)

Answer 641

If the conductor is connected to a circuit

Answer 642

So that it is more useful and safer to use

Answer 643

respond more rapidly to current surges than fuses do more reliable more sensitive can be reset (no need to replace)

Answer 644

wrap more coils around the iron core to create a stronger electromagnet that can attract the iron armature quicker and with more force

Answer 645

Wire from amplifier carries ac which makes the coil move backwards and forwards at the same frequency as the changing current. The coils mag.field and that of the magnet interact producing a force which is alternating due to the a.c current and thus changing mag.field of the amplifier wire. The paper cone is then forced to move which creates sound.

Answer 646

P = VI The heating effect of a high current would cause too much heat loss so current is reduced and if P is constant, then V must increase

Answer 647

Wrap wire around an iron core. When current is passed through the wire, a mag.field is created. This mag.field means that the wire magnetizes the iron core strongly.

Answer 648

Compass always points perpendicular to the wire (flow of current)

Answer 649

Can be made stronger Field strength can be varied Can be turned on/off

Answer 650

The motor wouldn’t spin as the current would short circuit across the ring and back to the power supply.

Answer 651

Made of carbon; soft and good electricity conductor Reduced friction between it and split ring commutator.

Answer 652

use a larger battery with a greater voltage add another battery in series thicker iron nail more coils of wire

Answer 653

how much compass deviates mass of iron filings picked up no of paperclips it can pick up

Answer 654

Experiment already carried out before and the iron still slightly magnetized She did not zero the balance when measuring the mass of iron filings picked up

Answer 655

It would rotate to vertical position and vibrate until it came to rest

Answer 656

Changes the direction of current flowing through the coil after every half turn by swapping the contacts at the DC supply

Answer 657

There is no induced voltage and no current flows b/c the flux lines are no longer being cut

Answer 658

It generated a mag.field to try and oppose that that is induced by the current in order to oppose the motion of the bar magnet’s mag.field

Answer 659

Transformers are devices that convert electricity from one voltage to another through electromagnetic induction.

Answer 660

two solenoids (coils) and a soft magnetic material (iron core) and an ac (alternating current supply)

Answer 661

Electricity from a power station passes through a step up transformer. This increases the voltage but decreases the current. This saves energy losses in the cables due to heating of the metal cables. The transmitted electrcity passes through a step down transformer which decreases the voltage but increases the current before it reaches the industrial or domestic users.

Answer 662

Vp / Vs = (No. of turns) Np / Ns

Answer 663

input power = output power or VP IP = Vs Is

Answer 664

Alternating voltage

Answer 665

a step up transformer

Answer 666

step down transformer

Answer 667

Has delocalised electrons that flow freely.

Answer 668

Has localised electrons that are held tightly in place.

Answer 669

gold, copper

Answer 670

rubber, wood, plastic

Answer 671

Applying a frictional force between two insulators, transferring electrons, giving a ‘permanent’ charge.

Answer 672

Bringing another charged object close to an insulator to create a ‘temporary charge’.

Answer 673

Because they are lightest and have the shortest distance to travel.

Answer 674

The insulators have become charged by friction The electrons have been transferred From rod to cloth

Answer 675

Transfer of electrons

Answer 676

As the balloon moves closer to the wall, the electrons inside the wall are repelled creative a positive surface closest to the balloon and a force of attraction.

Answer 677

the electron in the wall would move towards the the balloon as they are attracted and move to the closest surface. This means that the surface of the wall becomes negatively charged and attracts the balloon.

Answer 678

The generator rubs plastic and rubber together to produce a charge on the belt which is then transferred via a cone onto the conductor dome to produce a charged dome.

Answer 679

The vehicle is grounded and given a positive charge whilst the paint is given a negative charge. They attract each other, creating an even coat.

Answer 680

Paint droplets repel each other and are attracted to car creating even coat. East to pain odd objects. Less waste of paint.

Answer 681

To remove pollutants from the air.

Answer 682

smoke travels up precipitator and travels past strongly charged grid that causes particles to have a negative charge Further up the precipitator, positively charged plates attract the charged pollutants and collect them in collecting plates.

Answer 683

It can cause sparks which can then cause fires and explosions.

Answer 684

Friction from air resistance causes them to become statically charged

Answer 685

A copper wire can provide a low resistance path for the charge to travel to the ground and leave the plane.

Answer 686

The rate of flow of charge

Answer 687

current (I) = charge (Q) / time (t)

Answer 688

The energy transferred per unit of charge.

Answer 689

voltage (V) = energy transferred (E) / charge (Q)

Answer 690

Ammeter (in series)

Answer 691

Voltmeter (in parallel)

Answer 692

That the voltage is proportional to the current for a component with a fixed resistance.

Answer 693

The longer the wire, the greater the resistance, because there is a greater number of collisions involving the delocalised electrons

Answer 694

The thicker the wire the lower the resistance, therefore increasing the number of pathways for the delocalised electrons.

Answer 695

The higher the temp, the higher the resistance as ions can vibrate more, increasing NO. collision.

Answer 696

applying a frictional force between two insulators giving a ‘permanent’ charge

Answer 697

bringing another charged object close to an insulator to create a ‘temporary’ charge

Answer 698

the rate of flow of charge

Answer 699

the energy transferred per unit of charge

Answer 700

The higher the temperature the higher the resistance as ions can vibrate more, increasing collisions involving ions

Answer 701

The longer the wire the higher the resistance as there are a greater amount of collisions

Answer 702

The thicker the wire the lower the resistance as there are more pathways

Answer 703

It only allows current to flow in one direction.

Answer 704

Emits light when current flows in right direction

Answer 705

the resistance decreases

Answer 706

The resistance decreases

Answer 707

The resistance also increases, as the ions in the filament also gain more energy, meaning they vibrate more increasing the number of collisions.

Answer 708

is the same everywhere in the circuit

Answer 709

is shared between components

Answer 710

is the sum of resistance of components

Answer 711

is the sum of the current in each loop

Answer 712

is the same in each loop

Answer 713

from positive to negative

Answer 714

from negative to positive

Answer 715

green and yellow

Answer 716

directs current into ground in case of fault and current flows through casing

Answer 717

Amperes (Amps)

Answer 718

Transfer of electrical energy to heat energy and an increase in temperature (e.g. in a kettle’s element)

Answer 719

Alternating Current

Answer 720

Voltage of cell

Answer 721

They are inversely proportional to one another

Answer 722

V=E/Q=P/I=IR

Answer 723

The rate of flow of charge

Answer 724

Direction and intensity of a magnetic field

Answer 725

A magnetic field in the anticlockwise direction around the wire

Answer 726

A force is exerted

Answer 727

strength of magnetic field; current

Answer 728

Use a vacuum; convection needs a fluid to work in. Use trapped gas or liquids which restrict motion of convection currents.

Answer 729

Use shiny surfaces which will reflect the IR rays away. Shiny surfaces are also poor radiators of heat; black-bodies absorb and radiate the most heat.

Answer 730

A single coil of wire is in a magnetic field. A current passes through the wire which makes it move to and fro between 180°. A split ring commutator ensures that the current continues to change direction (otherwise the coil wouldn’t spin)

Answer 731

Increase number of turns on the coil; Increase number of cells in battery; increase the strength of the magnetic field.

Answer 732

If you make a left-hand gesture where the thumb, index finger and middle finger are all orthogonal to one another (perpendicular), if the index finger is the direction of the magnetic field (North to South), and the middle finger is the direction of the current, the thumb will be pointing in the direction of the force exerted on the wire.

Answer 733

If you make a fist with the thumb pointing upwards with your right hand, if the thumb is the direction of the current, the fingers will be pointing in the direction of the magnetic field produced surrounding the wire.

Answer 734

A conducting coil moves in a changing magnetic field induces a voltage; since the coil in which the voltage is being induced will be spinning, the electrical connections are made by the carbon brushes which slide over the commutator rings.

Answer 735

Vp/Vs = Np/Ns = Is/Ip

Answer 736

It decreases the voltage and increases the current.

Answer 737

It increases the voltage and decreases the current.

Answer 738

Because using a step up transformer, the current will decrease, and power lost = I^2R, so the current needs to be as low as possible to minimise power lost.

Answer 739

A statically charged drum is exposed to light, reflected from the document to be copied, which discharges the drum everywhere except where the the dark print does not reflect the light. The charged parts of the drum attract the toner which is then bonded (by heat) to the paper.

Answer 740

The ink droplets are charged and are allowed to be directed to particular places on the paper by deflecting them between charged plates.

Answer 741

The droplets of paint are given a static charge and the object to be painted is given the opposite charge. Therefore, the paint droplets will be attracted to the surface of the object and they will be evenly spread out from each other - this minimises paint used.

Answer 742

Energy transferred per unit charge passed Volts = energy transferred ÷ charge

Answer 743

Rate of flow of charge Amps = charge ÷ time

Answer 744

Ohms = voltage ÷ current More resistance = less current.

Answer 745

Watts = energy ÷ time Watts = voltage x current

Answer 746

straight line through origin ∴ V directly proportional to I constant gradient ∴ constant resistance constant resistance because constant temperature

Answer 747

Energy transferred per unit charge passed Volts = energy transferred ÷ charge

Answer 748

Rate of flow of charge Amps = charge ÷ time

Answer 749

Ohms = voltage ÷ current More resistance = less current.

Answer 750

Watts = energy ÷ time Watts = voltage x current

Answer 751

straight line through origin ∴ V directly proportional to I constant gradient ∴ constant resistance constant resistance because constant temperature

Answer 752

s shape, with rotational symmetry at bottom gradient steep ∴ low resistance. This is due to low temperature, so the bulb will also be dimmer at top gradient shallow ∴ high resistance. This is due to high temperature, so bulb will be bright

Answer 753

high resistance in one direction so current can only go in other direction only turns on at 0.6V

Answer 754

A resistors which varies with temperature. Cold = high res. Warm = low res.

Answer 755

A resistor whose value depends on light intensity. Dark = high res. Light = low res.

Answer 756

Resistance Current Voltage Power

Answer 757

Negative to positive

Answer 758

Positive to negative

Answer 759

Dc, e.g. Cell, only goes one way can’t change direction Ac, e.g. Mains, goes both ways ∴ can change direction, above and below axis

Answer 760

they slow down current ∴ the KE of the electrons turned into thermal energy can be used in appliance, e.g. Hair dryers

Answer 761

use an ammeter and measure current w and wo these elements. measure different voltage levels using a voltmeter w these elements

Answer 762

Series: current is the same Parallel: current divided by num of components

Answer 763

x axis is time base- time per cm. Can find freq of wave: 1/time y axis is y-gain. This is volts per cm. We can work out the amplitude of the wave, e.g. If y-gain is 2 V/cm, and it is 3 cm high, then V = 6

Answer 764

Longest pin ∴ goes in first and open other holes If live wire becomes loose and touches the case, case becomes live. If you touch case, instead of current going through you, it takes path of least resistance through case, earth wire and to the ground ∴ creates a large current, which blows the fuse

Answer 765

No external bits of metal in appliance ∴ case can’t become live ∴ don’t need earth wire

Answer 766

Flex is plastic coating on wire going in, as its an insulator Cable grip: holds in flex and keeps it down

Answer 767

* if current going through it is too large it melts causing gap in circuit, thus preventing fire Comes in 3A, 5A, and 13A. Use smallest possible, but only acc to 10%

Answer 768

spring loaded switch held closed by soft iron bolt. An electromagnet is turned on if I too large and pulls bolt away ∴ switch opens and circuit breaks. more reliable (fuse only acc to 20%) more sensitive switch can be reset unlike fuse which breaks and so must be replaced respond mor rapidly to current surges than fuses

Answer 769

Pros: * can disconnect or connect new elements without disrupting other elements, e.g. Can turn off a light without all the lights in your house going off * if one part breaks, it wont all. Current can flow through other parts Cons: * can’t increase or decrease the voltage * requires lots of wires

Answer 770

Pros: * more devices, the higher the voltage * don’t overheat easily ∴ better around flammable things like clothes Cons: * if one part breaks, it all breaks * greater the num components, higher the resistance

Answer 771

ampere / amps or A

Answer 772

The rate of flow of charge OR the number of coulombs passing a point in a circuit per unit time (It is not the speed of the electrons!)

Answer 773

1 A = 1 Coulomb per second

Answer 774

Volts or V

Answer 775

It is the energy per unit charge either supplied by a cell, or transferred to a component.

Answer 776

1 V = 1 J/C 1 volt = 1 joule per coulomb

Answer 777

a measure of how much voltage is needed per amp of current. It is a measure of the is a measure of the tendency of a material to resist the flow of an electrical current.

Answer 778

1 W = 1 J/s I Watt = 1 joule per second

Answer 779

V=E/Q Voltage = Energy / Coulomb Voltage lost across a component is a measure of the energy lost across the component per coulomb

Answer 780

The energy transferred from chemical store to electrical in the wires per coulomb

Answer 781

Series circuit Only one path or branch in the circuit

Answer 782

battery/two cells & solar cell

Answer 783

variable resistor

Answer 784

thermistor

Answer 785

Light emitting diode

Answer 786

Light dependent resistor

Answer 787

Current is conserved in all circuits Series - current is the same everywhere in the circuit Parallel - current splits between the branches- current into a junction equals current out of a junction

Answer 788

Current is conserved in all circuits Series - current is the same everywhere in the circuit Parallel - current splits between the branches- current into a junction equals current out of a junction

Answer 789

Series- voltage is shared - VCell = V1 + V2 Parallel - each bulb gets the full voltage of the cell - Vcell = V1 = V2 Bulbs in parallel are brighter = both have 3V across them (brighter) Bulbs in series have 1.5 v across each (dimmer)

Answer 790

V = IR I = V / R as resistance decreases, the current increases for the same voltage The second circuit draws a larger current from the cell, bulbs are in parallel and the total resistance is smaller than the first circuit (series circuit)

Answer 791

Voltage is shared between bulbs in series Less voltage across cell therefore bulb is dimmer.

Answer 792

circuit with two bulbs in series - has larger resistance V=IR I = V/R as resistance increases, current decreases for same voltage

Answer 793

Current is the same everywhere in a series circuit

Answer 794

Adding bulbs in parallel decreases the total resistance V=IR I = V / R as resistance decreases, current increases for the same voltage

Answer 795

As light intensity increases, resistance decreases

Answer 796

Circular field shape field lines getting futher apart- field getting weaker as you move away from the wire

Answer 797

Use the right hand grip rule Thumb- direction of current Fingers- wrap in direction of magnetic field (clock wise or anti-clockwise)

Answer 798

1) wrap a wire around an iron nail 2) connect a cell across the wire

Answer 799

1- more turns 2- increase the current 3- add an iron core

Answer 800

More wire- stronger field The closer the magnetic field lines the stronger the field. iron filing will line up more easily and more closely together in a stronger magnetic field.

Answer 801

Thumb- up and in direction of current Finger wrap in direction of magnetic field.

Answer 802

Place compasses around the wire The compass will point in the direction of the magnetic field

Answer 803

The direction of the magnetic field is reversed.

Answer 804

dot means out of the page cross means into the page

Answer 805

Fingers- wrap your fingers in the direction of the current Thumb- will point to the North end of the solenoid

Answer 806

Stronger magnetic field

Answer 807

Iron is magnetically soft- the domains in iron line up easily - it can magnetise and demagentise easily Steel is magnetically hard- the domains do not line up easily- it cannot magnetise easily and it can be used to make permananet magnets because it also does not easily demagnetise

Answer 808

The moment the iron armature moves to the right this creates a _break in the circuit- t_he circuit is no longer complete. The current drops to zero and the magnetic field around the electromagnet disappears. The iron armature is no longer attracted and springs back to the left The armature completes the circuit again and the whole cycle repeats alowing the bell to repeatedly sound.

Answer 809

7. No force at all Note: Particle is moving parallel to the field- no force.

Answer 810

Thumb = Motion First finger (index) = Field Second finger = Current

Answer 811

When coil is at 90º, the current in the coil reverses due to the commutator and brushes. Current continues to travel IN on the left and OUT on the right 8 Using LHR- left side of coil still experiences an upward force and the right hand side still experiences a downward force Coil continues to rotate clockwise

Answer 812

The needle with move to the right Reversing the direction of the magnet, reverses the induced current

Answer 813

Electromagnetic induction

Answer 814

The magnet is moving (thuMb- MOVEMENT) The magnetic field lines of the magnet are cutting the wires of the coil at 90º - (First finger- FIELD) This induces a current in the coil - (seCond finger- CURRENT)

Answer 815

Wire is moved downward (thuMb - MOVEMENT) The wire cuts the magnetic field lines at 90º - First finger- FIELD) This induces a current in the wire- (seCond finger- CURRENT)

Answer 816

The needle will move to the right Reversing the direction of the movement of the wire will reverse the direction of the induced current.

Answer 817

A large current would be induced

Answer 818

A large current would be induced

Answer 819

A large current would be induced

Answer 820

More turns in the coil Stronger magnet Move the magnet faster

Answer 821

Magnet is moved (thuMb- MOVEMENT) Magnetic field lines around magnet cut the coil at 90º (First finger- FIELD) Due to LHR a current is induced in the coil (seCond finger- CURRENT)

Answer 822

Wire is moved (thuMb- MOVEMENT) 90º to a magnetic field (First finger- FIELD) Due to LHR a current is induced in the wire (seCond finger- CURRENT)

Answer 823

Current carrying wire (seCond finger- CURRENT) 90º to magnetic field (First finger field) Using LHR this creates a force to the left- wire moves left (thuMb movement)

Answer 824

north pole and south pole

Answer 825

The magnetic field is strongest at the poles, the field lines are close together at the poles indicating a stronger field.

Answer 826

Place the bar magnets so that the N pole of one magnet is facing the S pole of the other. Move them so that they are close but not touching There is a uniform field between the poles

Answer 827

Uniform field Magnetic field lines are parallel AND evenly spaced

Answer 828

A region of space where a magnetic material experiences a force.

Answer 829

neutral point

Answer 830

Like poles repel Unlike poles attract

Answer 831

Magnetically hard- difficult for domains to align in a field (also difficult for domains which are lined up to de-align) Magnetically soft- easy for domains to align in a magnetic field and then de-align when field is removed.

Answer 832

Magnetically hard- so that it does not lose its magnetism easily

Answer 833

Pace paper over top the magnet Sprinkle iron filing on the paper Tap the paper to help the iron filings line up in the field

Answer 834

The nail is attracted to the N-pole The domains in the iron nail line up (point away) in the field creating a S-pole at the top of the nail closest to the magnet. (Magnetism is induced in the iron nail) Opposite poles attract and the nail sticks to the magnet.

Answer 835

Magnetised- domains are lined up De-magnetised- domains are randomly arranged

Answer 836

place a magnet on a piece of paper place a plotting compass at one corner of the N-pole of the magnet draw a dot where the compass is pointing. move the compass forward so that the tail is adjacent to the point you just plotted draw another dot where the compass is pointing Continue this until you reach the S-pole and connect the dots with a smooth curve. Repeat steps 3-6 drawing multiple field line around the magnet

Answer 837

Stroke the iron nail with a magnet for several minutes. This will align the domains in the iron nail and magnetise it.

Answer 838

Heat it, hammer it or drop it repeatedly. This will de-align the domains (demagnetise it)

Answer 839

North to South OUT of the North INTO the South