P6 - Electricity For Gadgets Flashcards

Question 1

Q

P6 - Electricity For Gadgets

What is current?

Answer

A

Flow of charge (electrons) round circuit. Only flows through a component if there is a voltage across that component. Measured in amps, A.

Question 2

Q

P6 - Electricity For Gadgets

What is voltage?

Answer

A

It pushes the current around. It is measured in volts V.

Question 3

Q

P6 - Electricity For Gadgets

What is resistance?

Answer

A

Anything in the circuit that reduces current and is measured in ohms.

Question 4

Q

P6 - Electricity For Gadgets

What causes resistance?

Answer

A

Collisions in a conductor. Electrons flow through a conductor and collide with metal atoms causing resistance. Collisions cause atoms to vibrate and more they get in way. Increased collisions means increased resistance and temperature of conductor.

Question 5

Q

P6 - Electricity For Gadgets

What is resistance like in longer wires?

Answer

A

More resistance, less current. Because longer wires have more atoms - electrons will collide.

Question 6

Q

P6 - Electricity For Gadgets

What is a variable resistor?

Answer

A

(Or rheostat) is a resistor whose resistance can be changed. Great for controlling current.

Question 7

Q

P6 - Electricity For Gadgets

What are variable resistors used for?

Answer

A

Controlling speed of motors and brightness of bulbs. Turning resistance down increases speed of motor and brightness of bulb.

Question 8

Q

P6 - Electricity For Gadgets

What does the voltage current graph look like/show for different resistors?

Answer

A

Current through a resistor at a constant temperature is proportional to voltage. Different resistors have different resistances. Straight line graphs are for ohmic resistors which have a constant resistance.

Question 9

Q

P6 - Electricity For Gadgets

What is the voltage current graph like for a filament bulb?

Answer

A

As current increases, temperature of filament increases (hence curve). Components with resistance that changes known as non-ohmic resistors.

Question 10

Q

P6 - Electricity For Gadgets

What is the total resistance in a series circuit?

Answer

A

Sum of individual resistors

Question 11

Q

P6 - Electricity For Gadgets

How is a circuit with resistors in parallel different?

Answer

A

Always less total resistance than branch with smallest resistance. Circuit has higher current.

Question 12

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P6 - Electricity For Gadgets

What is the rule for voltage across a pair of resistors?

Answer

A

Larger share of total resistance, larger share of total voltage.

Question 13

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P6 - Electricity For Gadgets

What is the output of the potential divider?

Answer

A

Point between two resistors. Output voltage can be varied by swapping one or both resistors for variable resistor.

Question 14

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P6 - Electricity For Gadgets

How are potential dividers useful?

Answer

A

Allows you to run a device that requires a certain voltage from a battery of a different voltage.

Question 15

Q

P6 - Electricity For Gadgets

What is an LDR?

Answer

A

Light Dependent Resistor - in bright light resistance falls, in darkness resistance is highest. Useful for devices like automatic lights and burglar detectors.

Question 16

Q

P6 - Electricity For Gadgets

What are thermistors?

Answer

A

In hot conditions, resistance drops. In cool conditions, resistance increases. Useful temperature sensors e.g. Car engine temperature gauges and electronic thermostats.

Question 17

Q

P6 - Electricity For Gadgets

How can you make a temperature sensor?

Answer

A

Using a thermistor and a fixed resistor in a potential divider.

Question 18

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P6 - Electricity For Gadgets

What is a transistor?

Answer

A

Electronic switches which use a small amount of current to control flow of a much larger current.

Question 19

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P6 - Electricity For Gadgets

What are the 3 parts of a transistor?

Answer

A

Base, collector, emitter

Question 20

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P6 - Electricity For Gadgets

What does the base do in a transistor?

Answer

A

Switch that controls flow of current, if no current applied to base, it stops current flowing through rest of transistor. When a small current is applied a larger current can flow through collector and emitter. A larger current would damage transistor.

Question 21

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P6 - Electricity For Gadgets

What does the collector do in a transistor?

Answer

A

Current flows into transistor through collector

Question 22

Q

P6 - Electricity For Gadgets

What does the emitter do in a transistor?

Answer

A

Current flows out of transistor through emitter.

Question 23

Q

P6 - Electricity For Gadgets

What is an LED?

Answer

A

A diode that gives out light

Question 24

Q

P6 - Electricity For Gadgets

What does a relay do?

Answer

A

2 circuits connected by a relay isolates the low voltage electronic system from high voltage mains often needed for the output device.

Question 25

Q

P6 - Electricity For Gadgets

What is an AND logic gate made from?

Answer

A

2 transistors

Question 26

Q

P6 - Electricity For Gadgets

Why is a relay safer?

Answer

A

For person using device because you can make sure that any parts that could come into contact with person are in low current sensing circuit.

Question 27

Q

P6 - Electricity For Gadgets

What is a magnetic field?

Answer

A

A region where magnetic materials (e.g. iron and steel) and also wires carrying current experience a force acting on them.

Question 28

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P6 - Electricity For Gadgets

Why is an LED better than an incandescent bulb?

Answer

A

It is better to show output because it uses less power and lasts longer.

Question 29

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P6 - Electricity For Gadgets

What is the rule for AND gates?

Answer

A

Each input (2 of them) can be either 1 or 0. An AND gate only gives an output of 1 if both the first and second output are 1.

Question 30

Q

P6 - Electricity For Gadgets

How does a relay work?

Answer

A

When switch in low-current circuit is closed, turns on electromagnet which attracts iron contact on rocker. Rocker pivots and closes contacts in high current circuit - and motor spins. When low-current switch is opened, electromagnet stops pulling, rocker returns and high current circuit is broken again.

Question 31

Q

P6 - Electricity For Gadgets

What is the rule for NOT gates?

Answer

A

A NOT gate just has one input - either 1 or 0.

Question 32

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P6 - Electricity For Gadgets

Where is a magnetic field created?

Answer

A

There is a magnetic field around a straight, current-carrying wire and it is made up of concentric circles with the wire in centre.

Question 33

Q

P6 - Electricity For Gadgets

What is the rule for NAND gates?

Answer

A

A NAND gate is a combination of NOT and AND. If AND gave an output of 0, a NAND would give 1 (or vice versa).

Question 34

Q

P6 - Electricity For Gadgets

What is an LED often connected to to protect it?

Answer

A

It is often connected in a series with a resistor to prevent it from being damaged by too large a current flowing through it.

Question 35

Q

P6 - Electricity For Gadgets

What rule is used to work out the magnetic field?

Answer

A

Right-Hand Thumb Rule (clenched fingers in direction of magnetic field)

Question 36

Q

P6 - Electricity For Gadgets

What is the rule for OR gates?

Answer

A

Each input (2 of them) can be either 1 or 0. An AND gate only gives an output of 1 if either the first or second is 1.

Question 37

Q

P6 - Electricity For Gadgets

What happens if you bend the current-carrying wire into a coil?

Answer

A

Circular magnetic fields around sides of loop reinforce each other at centre. More turns in coil, more individual loops reinforce each other even more.

Question 38

Q

P6 - Electricity For Gadgets

What is the name givento a coil of wire?

Question 39

Q

P6 - Electricity For Gadgets

What is an electromagnet?

Answer

A

A magnet whose magnetic field can be turned on or off with an electric current.

Question 40

Q

P6 - Electricity For Gadgets

What are the rules for NOR gates?

Answer

A

A NOR gate is a combination of a NOT and an OR. If an OR gives an output of 0, a NOR would give 1 (and vice versa)

Question 41

Q

P6 - Electricity For Gadgets

How can the strength of the magnetic field around a solenoid be increased?

Answer

A

Add a ‘soft’ iron core in middle of coil.

Question 42

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P6 - Electricity For Gadgets

How can the strength of the electromagnet be increased?

Answer

A

By adding more turns to the solenoid.

Question 43

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P6 - Electricity For Gadgets

What happens when a current-carrying wire is put between magnetic poles?

Answer

A

2 magnetic fields affect one another - result is a force on wire.

Question 44

Q

P6 - Electricity For Gadgets

What happens if the current-carrying wire runs along the magnetic field?

Answer

A

It won’t experience any force at all.

Question 45

Q

P6 - Electricity For Gadgets

What happens to the current-carrying wire to get the full force?

Answer

A

Wire has to be at 90 degrees (right angle) to magnetic field.

Question 46

Q

P6 - Electricity For Gadgets

When does the force on a current-carrying wire get stronger?

Answer

A

If the current or magnetic field is made stronger.

Question 47

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P6 - Electricity For Gadgets

What direction does the force act on a current-carrying wire?

Answer

A

Force always acts in same direction relative to magnetic field of magnets and direction of current in wire. Changing direction of either magnetic field or current will change direction of force.

Question 48

Q

P6 - Electricity For Gadgets

What does Fleming’s Left Hand Rule tell you?

Answer

A

Which way force acts in a current carrying wire.

Question 49

Q

P6 - Electricity For Gadgets

What 4 factors speed up the simple electric motor?

Answer

A

More current, more turns on coil, stronger magentic field, a soft iron core in coil.

Question 50

Q

P6 - Electricity For Gadgets

What does the first finger tell you in Fleming’s LHR?

Answer

A

Direction of field (magnetic)

Question 51

Q

P6 - Electricity For Gadgets

What happens to the forces on a current in a magnetic field if it is on a spindle?

Answer

A

Forces act one up and one down - rotates.

Question 52

Q

P6 - Electricity For Gadgets

What is the split-ring commutator?

Answer

A

A way of swapping conacts every half turn to keep motor rotating in same direction.

Question 53

Q

P6 - Electricity For Gadgets

What does the second finger tell you in Fleming’s LHR?

Answer

A

Direction of current

Question 54

Q

P6 - Electricity For Gadgets

How can the direction of the motor be reversed?

Answer

A

Either by swapping polarity of DC supply or swapping magnetic poles over.

Question 55

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P6 - Electricity For Gadgets

What does your thumb tell you in Fleming’s LHR?

Answer

A

Direction of force (motion)

Question 56

Q

P6 - Electricity For Gadgets

Which hand is used to find the force of a motor?

Answer

A

Left Hand

Question 57

Q

P6 - Electricity For Gadgets

Which hand is used to find the force of a generator?

Answer

A

Right hand

Question 58

Q

P6 - Electricity For Gadgets

How are motors made practical?

Answer

A

They use pole pieces which are so curved they form a hollow cylinder - coil spins inside cylinder. Curved pole pieces have a radial magnetic field which increases magnetic field strength around coil, so motor is more efficient.

Question 59

Q

P6 - Electricity For Gadgets

What is electromagnetic induction?

Answer

A

Creation of a voltage and maybe current in a wire which is experiencing a change in magnetic field.

Question 60

Q

P6 - Electricity For Gadgets

What happens to if a magnet/conductor is moved in the opposite direction?

Answer

A

Voltage/current will be reversed, similar to if (magnet) polarity is reversed.

Question 61

Q

P6 - Electricity For Gadgets

How can electromagnetic induction be generated?

Answer

A

Moving a magnet in a coil of wire OR moving a conductor (wire) in a magnetic field. Shifting magnet from side to side creates a bit of current.

Question 62

Q

P6 - Electricity For Gadgets

How is AC generated?

Answer

A

If you keep magnet/coil moving back and forth, produce a voltage that keeps swapping direction.

Question 63

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P6 - Electricity For Gadgets

What 4 factors affect the size of the induced voltage?

Answer

A

Strength of magnet. Area of coil. Number of turns on coil. Speed of movement.

Question 64

Q

P6 - Electricity For Gadgets

How is AC generated by turning a magnet?

Answer

A

Turning a magnet end to end in a coil creates a current that lasts as long as you spin magnet. As magnet turns, magnetic field through coil changes - this change in magnetic field induces a voltage which makes a current flow. After 1/2 turn, magnetic field direction reverses and this reverses voltage, current flows in opposite direction around coil of wire. Keep turning magnet in same direction and voltage changes each 1/2 turn - AC.

Answer 64

A

If turned faster, higher peak voltage, but also higher frequency - because magnetic field is reversing more frequently.

Answer 65

A

Rotate a coil in a magnetic field. As coil/magnet spins, current is induced in coil. Current changes direction every half turn.

Answer 66

A

Slip rings and brushes so contacts don’t swap every half turn.

Answer 67

A

More peaks and higher overall voltage.

Answer 68

A

Different type of generator. They rotate magent instead of coil to produce AC.

Answer 69

A

Rotating an electromagnet in a coil of wire.

Answer 70

A

Adding more turns to electromagnetic coil.

Answer 71

A

By rotating electromagnet coil faster.

Answer 72

A

2 coils of wire round iron core. Used to change size of an alternating voltage. There are 3 types.

Answer 73

A

They step up voltage. Have more turns on secondary coil than primary coil.

Answer 74

A

Step voltage down. Have more turns on primary coil than secondary.

Answer 75

A

Don’t change voltage at all. Have same number of turns on primary and secondary coils.

Answer 76

A

Primary coil produces magnetic field which stays within iron core, meaning nearly all passes through secondary coil and hardly any lost. Because AC in primary coil, current in iron core constantly changing direction - it is a changing magnetic field and this is felt by secondary coil. Changing field induces an alternating voltage in secondary coil (with same frequency) - electromagnetic induction.

Answer 77

A

Relative number of turns on 2 coils determines whether voltage induced in secondary coil will be greater or less than voltage in primary.

Answer 78

A

Only work with AC. If supplied DC, get nothing from secondary coil. Would be a magnetic field in iron core, but wouldn’t be constantly changing so there’d be no induction in secondary coil because you need a changing field to induce a voltage.

Answer 79

A

It is 100% efficient

Answer 80

A

VpIp = VsIs

Answer 81

A

Power = voltage x current P = V x I

Answer 82

A

Primary voltage ÷ secondary voltage = number of turns on primary ÷ number of turns on secondary

Answer 83

A

Either a high voltage or high current

Answer 84

A

Loss (heat) due to resistance of cables (and transformers)

Answer 85

A

Power loss = current² x resistance P = I²R

Answer 86

A

If current is 10x bigger, losses will be 100x bigger. Makes it cheaper to boost voltage to 400,000V and keep current very low.

Answer 87

A

For efficient transmission

Answer 88

A

In some mains circuits in home, such as bathroom shaver socket.

Answer 89

A

Safety. Mains circuit connected to earth so if you touch live parts and ground, you complete circuit. Isolating transformers allow shaver to be used without being physically connected to mains. Minimises risk of live parts touching earth lead - less risk of electrocution.

Answer 90

A

Only let current flow freely in one direction - very high resistance in other direction. Can tell direction of current from circuit symbol (triangle points in direction of current)

Answer 91

A

Semiconductors such as silicon, meaning they can conduct electricity, just not as well as a conductor. 2 different types of silicon joined together at a p-n junction.

Answer 92

A

1/2 diode made from silicon - impurity added to provide extra free electrons (n = negative charge of electrons)

Answer 93

A

P = positive charge of holes. Different impurity added to this half so fewer free electrons than normal. Lots of empty spaces left by missing electrons - called holes.

Answer 94

A

Electrons and holes recombine where 2 parts of diode join. Creates region with no holes/free electrons, which acts as an electrical insulator.

Answer 95

A

Applying voltage in RIGHT direction means free holes and electrons have enough energy to get across insulating region to other side - CURRENT flows. Applying voltage in WRONG direction means free holes and electrons pulled away from insulating region so stay on same side - NO CURRENT FLOWS.

Answer 96

A

A single diode only lets through current in half of cycle.

Answer 97

A

Bridge circuit with 4 diodes. Current always flows through component in same direction, output voltage always has same sign.

Answer 98

A

By connecting it to source of voltage e.g. battery. Current flows around circuit and charge gets stored on capacitor.

Answer 99

A

Flow of current decreases.

Answer 100

A

When voltage is equal to that of battery, current stops and capacitor fully charged. Voltage across capacitor won’t rise above voltage of battery.

Answer 101

A

Capacitor discharges - flow of current is same for discharging as charging but current flows in opposite direction around circuit.

Answer 102

A

Smaller devices use less raw materials. Most customers like smaller devices.

Answer 103

A

More portable electronic devices available. More powerful and feature-filled devices produced.

Answer 104

A

Can be more complex to produce small devices, and more expensive.

Answer 105

A

Smaller devices can be more expensive - easier to lose.

Answer 106

A

What is current?

Answer 107

A

What is voltage?

Answer 108

A

What is resistance?

Answer 109

A

What causes resistance?

Answer 110

A

What is resistance like in longer wires?

Answer 111

A

What is a variable resistor?

Answer 112

A

What are variable resistors used for?

Answer 113

A

What does the voltage current graph look like/show for different resistors?

Answer 114

A

What is the voltage current graph like for a filament bulb?

Answer 115

A

What is the total resistance in a series circuit?

Answer 116

A

How is a circuit with resistors in parallel different?

Answer 117

A

What is the rule for voltage across a pair of resistors?

Answer 118

A

What is the output of the potential divider?

Answer 119

A

How are potential dividers useful?

Answer 120

A

What is an LDR?

Answer 121

A

What are thermistors?

Answer 122

A

How can you make a temperature sensor?

Answer 123

A

What is a transistor?

Answer 124

A

What are the 3 parts of a transistor?

Answer 125

A

What does the base do in a transistor?

Answer 126

A

What does the collector do in a transistor?

Answer 127

A

What does the emitter do in a transistor?

Answer 128

A

What is an LED?

Answer 129

A

What does a relay do?

Answer 130

A

What is an AND logic gate made from?

Answer 131

A

Why is a relay safer?

Answer 132

A

What is a magnetic field?

Answer 133

A

Why is an LED better than an incandescent bulb?

Answer 134

A

What is the rule for AND gates?

Answer 135

A

How does a relay work?

Answer 136

A

What is the rule for NOT gates?

Answer 137

A

Where is a magnetic field created?

Answer 138

A

What is the rule for NAND gates?

Answer 139

A

What is an LED often connected to to protect it?

Answer 140

A

What rule is used to work out the magnetic field?

Answer 141

A

What is the rule for OR gates?

Answer 142

A

What happens if you bend the current-carrying wire into a coil?

Answer 143

A

What is the name givento a coil of wire?

Answer 144

A

What is an electromagnet?

Answer 145

A

What are the rules for NOR gates?

Answer 146

A

How can the strength of the magnetic field around a solenoid be increased?

Answer 147

A

How can the strength of the electromagnet be increased?

Answer 148

A

What happens when a current-carrying wire is put between magnetic poles?

Answer 149

A

What happens if the current-carrying wire runs along the magnetic field?

Answer 150

A

What happens to the current-carrying wire to get the full force?

Answer 151

A

When does the force on a current-carrying wire get stronger?

Answer 152

A

What direction does the force act on a current-carrying wire?

Answer 153

A

What does Fleming’s Left Hand Rule tell you?

Answer 154

A

What 4 factors speed up the simple electric motor?

Answer 155

A

What does the first finger tell you in Fleming’s LHR?

Answer 156

A

What happens to the forces on a current in a magnetic field if it is on a spindle?

Answer 157

A

What is the split-ring commutator?

Answer 158

A

What does the second finger tell you in Fleming’s LHR?

Answer 159

A

How can the direction of the motor be reversed?

Answer 160

A

What does your thumb tell you in Fleming’s LHR?

Answer 161

A

Which hand is used to find the force of a motor?

Answer 162

A

Which hand is used to find the force of a generator?

Answer 163

A

How are motors made practical?

Answer 164

A

What is electromagnetic induction?

Answer 165

A

What happens to if a magnet/conductor is moved in the opposite direction?

Answer 166

A

How can electromagnetic induction be generated?

Answer 167

A

How is AC generated?

Answer 168

A

What 4 factors affect the size of the induced voltage?

Answer 169

A

How is AC generated by turning a magnet?

Answer 170

A

What do you get if you increase the speed of the magnet?

Answer 171

A

How does a generator work?

Answer 172

A

What do generators have instead of split-ring commutators?

Answer 173

A

What current do generators produce?

Answer 174

A

What do faster revolutions produce in a generator?

Answer 175

A

What are dynamos?

Answer 176

A

How is electricity in a power station generated?

Answer 177

A

How can the size of the output voltage be changed in a dynamo?

Answer 178

A

How can the size and frequency of the output voltage be changed in a dynamo?

Answer 179

A

What are transformers?

Answer 180

A

What is a step up transformer?

Answer 181

A

What is a step down transformer?

Answer 182

A

What is an isolating transformer?

Answer 183

A

How does a transformer work?

Answer 184

A

What determines the size of the voltage induced in the secondary coil in a transformer?

Answer 185

A

Why doesn’t a transformer work with DC?

Answer 186

A

What do you have to assume with transformers?

Answer 187

A

How can power in = power out be re-written?

Answer 188

A

What is the formula for power supplied?

Answer 189

A

What is the equation to calculate output voltage from a transformer?

Answer 190

A

What is needed to transmit a lot of power?

Answer 191

A

What is the problem with a high current?

Answer 192

A

What is the formula for power loss?

Answer 193

A

What is the significance of the I² in powerloss?

Answer 194

A

Why do transformers have to step the voltage up and down?

Answer 195

A

Where can isolating transformers be used?

Answer 196

A

What is the purpose of isolating transformers?

Answer 197

A

What do diodes do?

Answer 198

A

What are diodes made from?

Answer 199

A

What is the n-type semiconductor in a diode?

Answer 200

A

What is the p-type semiconductor in a diode?

Answer 201

A

What happens in the diode when there is no voltage?

Answer 202

A

Why is the direction very important when there is a voltage across a diode?

Answer 203

A

What is half-wave rectification?

Answer 204

A

What needs to be done to get full-wave rectification?

Answer 205

A

How do you charge a capacitor?

Answer 206

A

What happens to the flow of current after time in a capacitor?

Answer 207

A

What happens to a capacitor when the voltage across it is equal?

Answer 208

A

What happens if the battery is removed from a circuit with a capacitor?

Answer 209

A

What are the benefits to makers if electronic components get smaller?

Answer 210

A

What are the benefits to users if electronic components get smaller?

Answer 211

A

What are the drawbacks to makers if electronic components get smaller?

Answer 212

A

What are the drawbacks to users if electronic components get smaller?