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GSCE Physics Flashcards

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1
Q

What does a insulated appliance (e.g hairdryer) only have

A

live and neutral

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2
Q

examples of insulated appliances

A

blenders, coffee makers, blow dryers, drills, and other power tools.

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3
Q

Magnetism

A

Magnet exert force on another nearby
force strongest at poles
Domains: random directions->point in same directions
can magnetise material by
stroking it with permanent magnet
If you hit magnet with hammer, loses magnetism

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4
Q

Magnetic materials

A

Affected by magnets
Attracted to either pole
Iron, steel, nickel, cobalt

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5
Q

Permanent magnet

A

Always cause force on other magnets/magnetic materials
always has poles/produces own magnetic field

attract/repel other permanent magnet
attract magnetic material (induced) but not repel
-Check permanent by if it can repel another magnet
examples: bar magnets, horseshoe magnets

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6
Q

Induced magnet

A

only becomes magnet when placed in magnetic field - temporary
Most/all magnetism quickly lost when removed from field
only attracted to other magnets, not repelled
Always causes force of attraction
E.g iron fillings

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7
Q

Magnetic field

A

Region around a magnet

when a force acts on another magnet/magnetic material

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8
Q

Magnetic field lines

A
  • field lines never cross eachother
  • closer lines, stronger field
  • arrowheads show direction of force
  • arrowheads point from N-S Pole of magnet
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9
Q

Plotting compass

A

Contains small bar magnet on pivot (can rotate)
Needle always points South/North Pole of magnet/in direction of magnetic field/lines up w earth magnetic field lines

  • place it near magnet on paper
  • mark direction needle points to
  • move compass to many different positions in magnetic field
  • mark direction needle points to each time
  • join points to show field lines
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10
Q

Earth’s magnetic field

A

Produced by convection currents in the earth’s core (iron and nickel)
plotting compass’s North Pole always lines up with Earth’s magnetic field lines and point to magnetic pole

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11
Q

Current carrying wires

A

Circular magnetic field around wire
Field can deflect needle of a magnetic compass
Strength increases if current is increased
greater distance from the wire, the weaker the magnetic field

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12
Q

Solenoid

A

Wire coiled up into a spiral shape
When electric current flows, the small magnetic fields in each coil add together= strong overall magnetic field. Strong and uniform
Factors: size of current, length of coil, number of turns, type of core (e.g iron)

shape of magnetic field similar to bar magnet

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13
Q

Motor effect

A

Force exerted on a wire carrying a current in a magnetic field which causes it to rotate

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14
Q

Fleming’s left hand rule
thumb- movement of force
Forefinger- field n to s
second finger- current + to -

A
  • permanent magnet field+ field of wire current combine and there is a force on wire
  • Current, magnetic field and force are all at right angles to one another
  • If current+ magnetic field parallel to eachother (same direction), cancels eachother out + no force is generated as wire not passing through any magnetic field limes
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15
Q

Electric motor

A
  • motor effect
  • permanent magnets in fixed positions
  • current carrying wire coil rotates as induced force on one side moves upwards and induced force of opposite side moves downwards
  • Split ring commutator changes current direction every half turn to keep it rotating
  • Conducting brushes reconnect w/ commutator after a half turn, current flows in different directions on each side of coil so each side experiences a force in opposite directions causing the motor to spin
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16
Q

Loudspeakers

Made of coil and magnet

A
  • motor effect
    -ac supplied to coil in loudspeaker, current creates electromagnetic field and makes electromagnetic, interacts with permanent magnet
    -variations in electric current in coil > causes variations in magnetic field produced by electromagnet - generates force
    Coil is attached to cone
    pushing cone outwards
    -direction of field reverses when current alternates repeatedly(flow in opposite direction) so force on cone pulled back.
    -cone vibrate in and out, creating pressure variations in air= forms sound waves
    ————-
    Headphones contain small loudspeakers
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17
Q

Electromagnet

A

When electric current flows in wire, creates magnetic field around wire which makes electromagnet
Can be turned on/off
reversed by reversing current
simple electromagnet: wire connected to power supply, coiled around magnetic material
Strength of field can be varied. stronger by: more turns to coil, iron core, Increasing current

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18
Q

Inducing a p.d

Electromagnetic induction

A

P.d needed to make electric current flow in circuit. P.d can be induced in conductor
when there is movement between conductor n magnetic field: coil wire moved into magnetic field/ magnet moved into coil of wire. induced p.d produces induced current if conductor is connected in complete circuit. Induced current creates magnetic field around itself
When magnet moves into/around coil of wire, induced magnetic field repels magnet back out of coil
Current reversed when magnet is moved out of coil/other pole of magnet moved into
Induced p.d/induced current increase if speed of movement/magnetic field strength/number of turns on coil is increased

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19
Q

Ac generator

Alternator

A

Device - produces a p.d
coil of wire rotating in magnetic field, two slip rings that rotate with coil (connects coil to an external circuit so alternating p.d produced). Graphite brushes sit on slip rings to complete circuit

As one side of coil moves up through field, a p.d induced in one direction. As rotatating continues and side of coil moves down, induced potential difference reverses direction
Alternator produces current constantly changing/alternating.
Max potential difference/current increased by: coil rotated faster, stronger magnet, increase strength of magnetic field, Increasing number of turns on coils= higher pd is induced causing more current to flow. Frequency of ac increased.

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20
Q

Ac graph

A

0- coil move parallel to direction of field so no p.d induced
90- coil moving at right angle to direction of field so induced p.d at its maximum
180- coil moving parallel again.
270- coil moving at right angle so max but p.d travels in opposite direction to B
360- back at starting point, done full rotation. coil move parallel to direction of field, no p.d induced

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21
Q

Dc generator

Dynamo

A

Device produces p.d
Consists of coil of wire rotating in magnetic field but uses a split ring commutator
spit ring commutator changes the coil connections every half turn
as induced potential about to change direction, connections are reversed so current to the external circuit always flows in same direction

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22
Q

Dc graph

A

0- coil moving parallel to direction of magnetic field, no p.d induced
90- coil moving right angles to field direction, induced p.d at max
180- coil moving parallel
270- coil moving right angle, induced p.d at max but p.d travels in the same direction as B
360- back at starting point, full rotation, coil parallel

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23
Q

Microphone

A

-electromagnetic induction
Converts pressure variations in sound waves into electrical signals (variations in current) in electrical circuits
uses generator effect to induce changing current from pressure variations of sound waves
-pressure variations in sound waves cause diaphragm to vibrate which causes vibrations in coil
-coil moves relative to a permanant magnet so p.d induced in coil
-coil part of complete circuit so induced p.d causes current to flow around circuit
-changing size and direction of induced current matches vibrations of coil
-electrical signals generated match the pressure variations in the sound waves

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24
Q

Generator effect

A

When motion between a conductor and magnetic field creates electricity
E.e a magnet moved into a coil of wire
——————————
wire moved cut magnetic field lines p.d induced across wire causing current flow in wire (electromagnetic induction). Increased= stronger magnet, wire moved faster, more wire/coils. Direction current reversed if magnetic field reversed/ wire moved in opposite directions
——————————————
When magnet goes onto the coil the needle moves to the right
When the magnet does not move needle stays on 0
When magnet leaves coil, ammeter needle moves to left
If magnet moves faster into coil, needle moves further to right
If S Pole was pushed into coil, needle would move to the left

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25
Q

Transformer

A

Devices that can change p.d of alternating current
Step-up increases p.d, Step-down reduces p.d
Made from two coils of wire, primary coil from ac input, and secondary coil to ac output, coils are not electrically connected, both wound around iron core. Easily magnetised and can carry magnetic fields from primary coil to secondary.
-primary coil connected to ac supply
-primary p.d drives ac through primary coil
-primary coil current produces a magnetic field, which changes as current changes
-iron core increases strength of magnetic field
-changing magnetic field induces a changing p.d in secondary coil
-induced potential difference produces an alternating current in external
Transfers can only work with alternating current

risks:
high voltages can be produced
- insulate secondary coil, use very low voltages on primary coil

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26
Q

Calculating potential difference

A

ratio of p.d on transformers coils matches ratio of numbers of turns on coil
Energy is conserved
Power on primary side= power on secondary side

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27
Q

Charge

A

Positive/negative
All matter has charge
Property of all matter that causes a force when near another charge
Insulators don’t conduct charge as their electrons cannot flow throughout the material and are fixed
Conductors can conduct charge as their electrons are delocalised and can flow instead of being fixed

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28
Q

Static

A

Static charge only occurs when electrons build up on object
two insulators rubbed together- electrons transferred from one to the other. become charged as the electrons cannot flow

Protons do not move as they are tightly bound in the nuclei

two conductors are rubbed- electrons will flow in and out of them which cancels any overall effect so they remain neutral. Conductors allow the electrons to flow away, forming an electric current

Static charge can only build on on insulators
When static charge on a object is discharged, an electric current flows through the air which causes sparks. Discharge happens when enough charge builds up and the objects are close but not touching, the charge flows through the air from a highly negative object to a highly positive object to balance out the charges

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29
Q

Electrostatic force

A

Charged objects experience electrostatic force
Attractive or repulsive
Non contact
Greater charge and smaller separations result in greater force
Force is proportional to the inverse square of distance

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30
Q

Demonstrating charge

A

Charged object can attract an uncharged insulator
Charged object repels another charged object
Charged objects can attract small neutral objects near
Positive/negative charge on object attract/repel electrons within small objects, induces charge inside them causing them to be attracted
E.g balloons attract hair after being rubbed on a jumper, a stream of water will attractted by charged object due to induced attraction , two positively charged plastic robs repel, charged rod will attract bits of paper

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31
Q

Electric field

A

All charged objects have an electric field
Electric fields are created by electric charges
Can be attractive or repulsive
Exert forces on other charges
Any object with a electric charge will feel a force in a electric field
Closest where the field strength is greatest
Stronger the charge, the more field lines and the stronger the force is felt
Point in the direction away from positive charge towards negative charge
Can be demonstrated by sprinkling semolina onto castor oil
The particles of semolina line up in the fields generated by electro dies attached to a van de graaff generator

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32
Q

Electric field of charge diagram

A
  • lines drawn from pos to neg (arrows show force on a positive charge)
  • never cross
  • density of field lines on a diagram is indicative of the strength of the field
  • field gets weaker as distance from charge increases
  • arrows go out of the positive charge and into a negative charge.
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33
Q

Current

A

Rate of flow of charge
Needed for current to flow: source of p.d (e.g cell or battery) and a closed circuit that has a completed path for the charges to move through
Charge = current x time
Amps
Measured at any point on circuit by Ammeter placed in series to component
The current flowing through a component/in a circuit depends on its resistance and p.d across the component

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34
Q

Potential difference

A

Volts
Energy transferred between two points in a circuit
Voltmeter placed in parallel across a component
One volt is the potential difference when one coulomb of charge transfers one joule of energy

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35
Q

Series circuit

A

Closed circuit where the current only follows a single path
Only has one loop
Current same everywhere
P.d split between components, depends on resistance
Energy is conserved in circuits so..
Total p.dis the sum of potential differences across the individual components and the same as the potential difference of the cell
Total (net) resistance across all the components increases as more components are needed
Total resistance is R1+R2+

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36
Q

Parallel circuit

A

Has more than one loop
An electron will not pass through every component on its way round the circuit
If a component breaks, the current can still flow around the circuit through another loop so rest components keep working
Energy is conserved
Voltage is the same across each branch
Total current supplied is shared between components on different loops
The net resistance decreases as more components are added as there are more paths for the current to flow through. Worked out by dividing p.d of cell by total current for the circuit

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37
Q

Energy= charge x potential difference

A

When a charge moves through a potential difference, electrical work is done and energy is transferred

38
Q

Circuit symbols explanation

A

Switch- turn circuit on (closed) and off (open)
Lamp- electrical current heats filament in a bulb so it gives out light
Fixed resistor- limits the flow of electrical current, has a resistance that does not change
Variable resistor- resistance changed by moving the position of a slider. Used to limit and control flow of electric current
Thermistor- resistance depends on its temperature. Low temp=high res, high temp= low re. Used in thermostats, heat-activated fire alarms
Light-dependent resistor- resistance depends on light intensity. Low light= high res, high light= low res. Used in camera sensors, automatic security lights
Semiconductor diode- allows current to flow in one direction only, used to convert alternating current into direct

39
Q

Investigating the brightness of bulbs practical

A

Aim: to see how brightness of bulb change as they are connected in series/parallel, measure p.d and current across bulbs
Method:
- one bulb and a battery, series circuit, ammeter in series+voltmeter parallel with component, record if bulb is bright/dim, add another bulb into loop, record bulb’s brightness current and potential difference
Evaluation-
In series circuit, bulbs become dimmer as potential difference is shared equally across the bulb, current is same for all
In parallel circuit, each branch shows the same potential difference so bulbs on one branch will have the same relative brightness, the current for each bulb will add up to the current near the battery
Safety:
Overheating components e.g bulb. Burned fingers, scorched desk. Use heatproof mat, switch off between readers to ensure components don’t get too hot.
Blown bulb- shattered glass. never exceed max supply voltage

40
Q

Resistance

A

Electric wires are made of metal
Atoms in a solid metal are arranged in a regular lattice structure. The outer electrons from each atom are free to move through the structure, forming a current
However, they may collide with atoms or meet defects in the lattice which reduces the number of electrons flowing which reduces the current
Conductors have a low resistance, insulators have high resistance
Factors: heat, current, length of wire, thin/thick wire

41
Q

Ohm’s law

A

Current flowing through a resistor is directly proportional to potential’s difference
Provided the temperature remains constant

42
Q

Practical investigating current and p.d relationship

A

Difference for a resistor and filament bulb
-ensure power supply is set to zero at the start
-place variable resistor and fixed resistor in circuit
-place voltmeter parallel to fixed resister and ammeter in series to it
-record the readings
-use the variable resistor to alter the p.d
-record the new readings
-repeat, increasing the p.d each time
-repeat but with power supply reversed
-repeat but replace fixed resistor with a bulb
Evaluation:
For a fixed resistor, the potential difference is directly proportional to the current, so doubling the amount of energy into the resistoe results in a current twice as fast through the resister. Ohm’s law. Fixed resistor is a ohmic conductor (it obeys ohms law).
In a filament bulb, the current does not increase as fast as the potential difference. Doubling the amount of energy does not cause a current twice as fast. The more energy that is put into the bulb, the harder it is for the current to flow - the resistance of the bulb increases. As the p.d increases, the temperature of the thin wire inside the bulb does. Increases resistance of filament bulb.

43
Q

Semiconductor diode practical

A

Investigate relationship between current and p.d for a diode
-diode mist be protected with a suitable protective resistor
-set variable resistor to give the lowest potential difference
-record readings on voltmeter and millimetre (ammeter that’s capable of reading to +1 mA)
-alter variable resistor to increase potential difference by 0.2 V
-record the new readings
-repeat, increasing current each time
-repeat, reverse power supply connections
Evaluation: a semiconductor dioxide only allows current to flow in one direction. In one direction, the diode’s resistance is very large and no current will flow. In other direction, the diode’s resistance is smaller and current will flow.. in this direction, the diode’s resistance is very large at low potential differences. At high p.d, the resistance quickly drops and current begins to flow
Health and safety:
Heating of the resistance wire, burns to skin, do not touch resistance while whilst circuit is connected, allow time to cool

44
Q

Energy (work done)= power x time

A

Power is the rate of transfer of energy between energy stores or rate work is done
1 watt= 1 joule per sec

45
Q

How does resistance change?

A

As current increases: electrons have more energy. When these electrons flow through a resistor, they collide with the atoms in the resistor. This transfers energy to the atoms, causing them vibrate more, these increased vibrations make it more difficult for electrons to flow through the resistor, so resistance increases, and the current decreases
—————————————————
Temperature: normal wires - increased atoms vibrations when hot. thermistor- resistance is lower at higher temperatures
——————————-
Length- greater length, more resistance, lower current. Electrons have to make their way through more resistor atoms so it is harder than a shorter wire
—————————-
thinner/thick wires: thinner gives give greater resistance as less overall room for electrons to pass through atoms
——————
Light: for LDR, a greater light intensity= lower resistance, so resistance is greatest when dark.
——————-
Voltage: diode allows current to flow freely in one direction. In the opposite direction, they have a very high resistance so no current can flow.

46
Q

Physical quantity

A

A physical quantity is something that can be measured
Scalar quantity has only magnitude e.g distance, speed
Vector quantity has magnitude and direction e.g displacement (overall distance from a fixed point), velocity(total displacement/time)

47
Q

Motion in a circle

A

When a body moves in a circle, it’s direction is constantly changing so it has a constantly changing velocity
It must also be accelerating at some points. The force responsible for acceleration is centripetal force and it acts radially inwards towards the centre of the circle, it keeps the object moving in a circular path. E,g centripetal force due to friction between car’s tires and the road

48
Q

Speed, distance and time

A

Distance+ measure of how far an object moves
small=ruler/tape measure/trundle wheel. Large= GPS/aerial photography for measurement

Speed= rate of change of distance (distance travelled per unit time). Can be measured accurately with light gates

49
Q

Calculating average speed

A 
Average speed= total distance travelled/total time taken
When no units assume: 
Distance=meters
Average speed=m/s
Time=seconds
50
Q

Distance-time graphs

A 
Gradient=speed
Steeper the gradient=faster speed
If stationary= straight line \_\_\_
If constant speed= linear gradient line
If accelerating= curves upwards
If decelerating= curves downwards
51
Q

Velocity and acceleration

A

Velocity=m/s
Acceleration=m/s^2
Acceleration due to gravity is 10m/s^2 (resultant force =mass x acceleration due to gravity)

52
Q

Practical - investigating acceleration down a ramp

A

-set up ramp balanced on a wooden block at one end
-mark out 30cm at each end of ramp. Avoid making ramp too steep (causes trolley to roll too quickly, makes measuring difficult)
-release trolley from top of ramp, record time taken for it to reach the mark
-repeat from top of ramp but record time taken for it to reach end
-calculate speed
Health and safety= trolley falling, injury to feet, keep feet away from end of ramp

53
Q

Velocity-time graphs

A 
Gradient= acceleration
Area under graph=displacement 
A- accelerating
B-constant
C- decelerating
D=stationary
54
Q

Newton’s first law

A

Object remains in same state of motion unless a resultant force acts on it
When resultant force is zero: stationary object stays stationary, moving object continues to move at same velocity

Inertia= tendency of an object to continue in its current state (at rest or in uniform motion).
Inertial mass= ratio of force over acceleration. How difficult it is to change the velocity of an object

55
Q

Free body diagram

A

Models forces acting on an object

Resultant vector for two vectors at right angles
Pythagoras theorem
4^2+3^2=_/25=5

56
Q

Newton’s second law

A

Forces acting on a body are unbalanced the resultant force will NOT be zero and the object will speed up (accelerate), slow down (decelerate) or change direction.​
Force=mass x acceleration
If no units assume:
Force=newtons, mass=kg, acceleration=m/s^2
accerlation proportional to resultant force and inversely proportional to mass

57
Q

Newton third law

A

When two objects interact, they exert equal and opposite forces on eachother

58
Q

Terminal velocity

A

At terminal velocity, the object moves at steady speed in constant direction cuz resultant force is 0
Three stages of falling:
-object accelerates downloads due to force of gravity
-as it’s speed increases, frictional forces e.g air resistance/drag increase
-at terminal velocity, the weight of the object due to gravity is balanced by the frictional forces and resultant force=0
-opening parachute, air resistance increases, skydiver slows down until new lower terminal velocity is reached

59
Q

Momentum

A

Product of mass and velocity
Vector
he mass of an object multiplied by its velocity. ​
Momentum (kgm/s)= mass x velocity
In a closed system: Total moment before an event=total momentum after the event (Conservation of momentum)
Momentum is conserved in collisions and explosions

Calculate velocity from truck collision.
Mass after collision=10kg
2kg trolley=2x3=6kgm/s
8kg trolley=8x0=0kgm/s
Total momentum before collision=6+0=6kgm/s
velocity=momentum/mass
Velocity=6/10=0.6
60
Q

Work done by a force

A

Work is done when energy is transferred from one store to another
Also when force causes an object to move
When work is done against frictional forces acting on an object, object’s temperature increases
work done=force x distance

61
Q

Change of shape (deformation)

A

When a force acts on a object, object change shape by bending/stretching/compressing/combination of all
To change shape of a stationary object, there must be more than one force acting
Elastic deformation is reversed when force removed
Plastic deformation is not fully reversed when force is removed - there is a permanent change in shape

62
Q

Forces and extension

A

Extension happens when object increases in length
Compression happens when it decreases in length
Extension is directly proportional to force applied
E.g force doubled, extension doubles
Elastic limit - when elastic object is stretched beyond its elastic limit, the object does not return to its original length when the force is removed
Relationship between force and extension changes from linear to being non-linear

63
Q

Practical - investigate effect of forces on springs

A

-secure clamp stand to bunch using G-clamp/large mass on base
-use bosses to attach two clamps to the clamp stand
-attach the spring to the top clamp, and a ruler to the bottom clamp
-adjust the ruler so that is it vertical, and with its zero level with the top of the spring
-measure and record unloaded length of the spring
-have a 100g slotted mass carrier from the spring. Measure and record the new length of the spring
-add 100g slotted mass to the carrier measure and record new length of spring
-repeat
Accuracy: keep ruler vertical
Health and safety: equipment falling of table, heavy objects falling on feet could bruise or fracture, use a G-clamp to secure the stand, sharp end of spring recoiling if the spring sp breaks, damage to eyes, cuts to skin, wear eye protection, support and gently lower masses whilst loading the spring, masses falling to floor if the spring fails, heavy objects falling on feet could bruise or fracture, gently lower load onto spring and step back

64
Q

Gravity

A

All objects with mass have a gravitational field around them
A gravitational field is where a mass experiences a force
All matter has gravitational field that attracts other object
more mass an object has, the greater it’s gravitational field
N= kg x N/kg
gravity Force (also known as weight)= mass x GFS
GFS=10N/kg

65
Q

Weight

A

Refers to gravity force of planets and other bodies and the effect it has on objects
force that acts on a mass due to gravity when in gravitional field
Weight of object and mass are directly proportional
Non-contact force - Gravity exerts it’s force through a field
Weight of an object can be measured using calibrat3d spring-balance (Newton meter)

66
Q

Gravitational potential energy

A

When a object is lifted in a gravitational field, energy is transferred to a gravity store
J= kg x m x N/kg
GPE= mass x height x GFS

67
Q

Moments

A

A force or system of forces may cause a object to turn
A momen is the turning effect of a force
Moments act about a point in a clockwise or anti-clockwise direction
The point chosen could be any point on the object although is usually the pivot
Moment of a force= force x distance
Nm= N x m
Distance is the perpendicular distance from pivot to the line of action of the force

68
Q

Balanced objects and moment

A

If a object is balanced, the total clockwise moment about a pivot= total anti-clockwise moment

69
Q

Levers

A

Consist of: pivot, effort, load
Different types of levers:
EPL (e.g scissors), PLE (e.g wheelbarrow), PEL (tweezers)
Simple levers and rotation
As effort is applied to rotate one end about the pivot, the opposite end is also rotated about the pivot in the same direction which has the effect of rotating/lifting the load
Levers allow a larger force to act upon the load than is applied by effort
Easier to move large or heavy objects
The longer the lever, the further the effort acts from the pivot, the greater the force on the load, easier it is

70
Q

Gears

A

Gears are wheels with toothed edges that rotate on an axle or shaft
The teeth of one gear fit into the teeth of another gear which lets one gear turn the other
Meaning one axle or shaft can be used to turn
As one gear turns, the other must also turn
Where gears meet, the teeth must both move in the same direction
The forces acting on the teeth are identical for both gears but their moments are different
If a larger gear is driven by a smaller gear, the large gear will rotate slowly but have a greater moment
If a smaller gear is driven by a larger gear, the smaller gear will rotate quickly but have a smaller moment

71
Q

Pressure in fluids

A

Pressure is force per unit area
Determines the effect of a force on a surface
To increase pressure= increase force or reduce area the force acts on
To reduce pressure= decrease force or increase area force acts on
Calculating pressure
Liquids and gases are fluids- pressure in fluids cause a force normal to a surface. A force that is normal to a surface acts at right angles to it
Pressure= force normal to a surface/area of that surface
Pa= N/m^2

72
Q

Hydraulic systems

A

A machine that uses liquid to transmit a force
Pressure in liquid is the same everywhere in the system
Simplest type is made of two pistons connected by liquid filled pipe
If one piston is pushed, the force is transmitted through the liquid and the other piston moves
Liquids are used as they are more difficult to compress than gases so are better at transmitting forces - when a force is applied at one end of the system, it is easy transferred through the system

73
Q

Modelling the atom

A

Dalton’s model - tiny solid balls. Atoms cannot be broken down into anything simpler. The atoms of a given element are identical to eachother. Atoms of different elements are different from one another. During chemical reactions atoms rearrange to make different substances

Thomson model- plum pudding. discovered negative charged electrons. Atoms are mass spheres of positive charge. Electrons are scattered around inside.

Rutherford- nuclear model. Geiger marsden experiment tested plum pudding model. Aimed beams of positively charged alpha particles at thin gold foil sheet. Disapproved plum pudding model. Some alpha bounced back, passed, refracted. Means atoms are central positive charged nucleus with most of the mass. Electrons orbit the nucleus.
Bohrs model- using mathematical ideas, showed that electrons occupy shells/energy levels around nucleus

Atom is 1x10-10m
Radius of nucleus is much smaller than the radius of atom

74
Q

Density

A

Mass per unit volume of a substance

MDV

75
Q

Solids, liquids, gases

A

All matter consists of particles including atoms and molecules
Solids- particles are close together in a regular structure and vibrate around fixed position
Liquids- particles are close together but free to move past each other randomly
Gases- particles are far apart and move randomly in all directions

Density of a substance changes when it changes state. It’s mass does not change.
When solid to liquid, relatively small change in volume and density as particles still remain close together

76
Q

Practical - determining densities or different objects

A

Solid regular- top pan balance to record mass, ruler to measure length width height, calculate volume using low h, calculate density using MDV
Solid irregular- top pan balance to recor mass, fill displacement can until water is level with bottom of pipe, place measuring cylinder under the pipe so ready to collect displaced water, drop object into can and wait until no more water runs into cylinder, measure the volume of displaced water, calculate density MDV

Water- place empty measuring cylinder on top pan balance record mass, place liquid in measuring cylinder and measure new mass, record volume, mass of liquid= liquid in cylinder - empty cylinder on its own, calculate density MDV

Suggestions for improvement:
Top pan balance is only precise to +-1g, use a more precise balance
Displacement can may not be set up correctly each time - another added drop of water would cause some tod ripple out of spout before use so check that no water comes out before placing measuring cylinder under spout

Health and safety: water spilled from displacement can, spill and fall, work next to sink and have paper towels ready to mop up spills

77
Q

Changing state

A

Transferring energy to or from a substance can change its state
The number of particles does not change during a change of state, only their spacing and arrangement
Therefore conversation of mass
Changing state is physical change as process can be reversed
Chemical reaction is when changes cannot be reversed so easily

78
Q

Energy and tempwrature

A

Temperature is the measure of the average e kinetic energy of particles in a substance
Measured with thermometer or temperature sensor
The higher the temperature, the higher the average kinetic energy
Temperature does not show the energy store associated with an object

How do energy and temperature differ?
When energy is transferred by heating it can change the enety stored in system, change the physical state of the system, make chemical reactions occur
When enery is transferred to water in liquid state, water molecules gain kinetic energy and speed up. The larger the mass of water, the more energy needed to raise the temperature by a given amount. This is because more molecules need to have their speed changed

Change in temperature of a system depends on the amount of thermal energy transferred to the system, the mass of the substance and the nature of the substance itself

79
Q

Specific heat capacity

A

Measure of the amount of thermal energy needed to increase the temperature of 1kg of a substance by 1oC

80
Q

Specific latent heat

A

Changing the internal energy of a material will cause it change temperature or change state
The thermal energy to change the physical state is given by specific latent heat
Specific latent heat of a substance is the amount of energy needed to change he state of 1kg of a substance without changing its temperature

Each substance has two specific latent heat:
Latent heat of fusion: amount of energy neeed to freeze or melt the substance at its melting point
Latent heat of vaporisation: amount of energy needed to expose aye or condense the substance at its boiling point
Latent heat of vaporisation is usually greater than fusion as it takes more energy to boil a substance than to melt it

81
Q

Measuring specific heat capacity practical

A
  • place immersion heater into the central hole at top of weighted metal block
  • connect heater in series with an ammeter and in parallel with voltmeter
  • place thermometer into smaller hole. Add two drops of oil into the hole to make sure the thermometer is surrounded by hot material
  • insulate the block by wrapping it with cotton wool
  • record the temperature of the block
  • connect the heater to the power supply
  • record current a potential difference
  • after 10 mins, turn heater off. The temperature will still rise even though the heater has been turned off and then it will begin to cool. Record the highest temperature that it reaches

Health and safety: hot immersion heater and sample material, burnt skin, do not touch jester when switched on, position it away from edge of bench, allow time to cool before packing away equipment

82
Q

Particle motion

A

Particles on a gas move very quickly in random directions
Collisions frequently happen between particles, particles and the wall of the container, effect of collisions with the container is to produce a net force acting on the container walls, force acts at right angles to the container walls, which is detected as gas pressure, this pressure can be measured using a pressure gauge, collisions caused by a gas trapped inside a balloon causes forces to act outwards in all directions, giving the balloon its shape
A closed system is a system where no substances can enter or leave
P
A gas in a closed system can be compressed by reducing its volume which increases its pressure
Expanded by increasing its volume which decreases its pressure

83
Q

Pressure and temperature

A

Closed system: volume stays same, gas pressure increases as temp increases cuz gas particles travel faster. Collides with walls of container more frequently and with more force

In a fixed volume of gas, pressure is proportional to temperature

Abouslte zero (-273oC) where gas would have no pressure and particles would not be moving at all

84
Q

Pressure and volume

A

Closed system= temp says same, gas pressure increases as volume decreases
Same number of particles collide with walls of container more frequently as less space
Particles collide with same amount of force (as temp says same)

Boyle’s law :
Experiment: trapped air bubble at sealed end of a J shaped tube using liquid mercury and then added more mercy and observed what happened to volume of air bubble
discovered that higher the column of mercy in the left hand tube, the greater the force exerted on the trapped air, the smaller the bubble became as its pressure increased, Volume is inversely proportional to pressure

E.g if volume of container halved, pressure doubled
Pressure x volume= constant
Pa x m^3

85
Q

Atmospheric pressure

A

Atmosphere exerts pressure on the earth surface and objects placed in atmosphere

Decreases as altitude (height above the surface of planet) increases
as number of gas molecules in a given volume of air decreases, frequency of collisions with objects in the air decreases, the pressure decreases

86
Q

Work and energy

A

Pressure can be increased:
increase temp (increases frequency and force of collisions)
decrease volume - increase frequency of collisions but not the force

A force applied to the particles in a gas a causes a transfer of energy
Work is done on the gas to compress it
Work done= force x distance
J= N x m
Mechanical work transfers energy from the person or machine’s store of chemical energy to thermal energy store of the gas

The volume of the gas decreases so the pressure increases, this is because the gas particles are moving in less space, so they collide with the container walls more often

The moe rather of gas is not fixed in most applications and increased pressure leads to increase in temp
so an increase in enety store of gas (kinetic energy) means temp must increase as it’s the measure of the average KE of particles

87
Q

Pressure in liquids

A

Particles in liquids close together
Exert pressure by colliding w eachother and w objects and container walls
Liquid pressure exerted equally in all directions
Pressure increases w depth and density of liquid
deeper object submerged in liquid, greater pressure.
As particles in any part are being squashed by weight of liquid above them. Greater depth, greater weight of liquid above
For a given volume of liquid, the greater density of the liquid, the greater it’s mass, when comparing the pressure in liquids of different densities the pressure is greater at the same height in the densest liquid because there is a greater weghr of liquid pushing down
Pressure due to column of liquid = height of column x density of liquid x GFS
Oa= m x kg/m^3 x N/kg

88
Q

Floating and sinking

A

object partially submerged in liquid experiences upwards force (upthrust)
float if upthrust=weight of object
Sink if upthrust less than weight
also depends on area+density of object

89
Q

Total pressure

A

The total pressure exerted on any submerged object= liquid pressure + atmospheric pressure

90
Q

Types of force

A

Electrostatic- repulsion or attraction due to charge
Gravity - all masses attract each other
Magnetism - repulsion or attraction of magnets
Normal contact force - repulsive force when two objects touch each other
Friction - acts when two surfaces move past each other - always on the opposite direction to movement

91
Q

Energy stored in a spring

A

Work is done when a spring is extended or compressed
Work done is equal to elastic potential energy stored provided plastic deformation has not happened
J=0.5 x n/m x m^2
J=0.5 x spring constant x extension^2

A-level Physics, Astronomy & Engineering (1 decks)

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