Physics Paper 2 Consolidation

Question 1

Describe the relationship between current and voltage in a filament lamp.

Answer 1

• Current increases as voltage increases
• Not directly proportional
• Decreasing gradient as voltage increases
• Non-linear

Question 2

State 2 practical ways to reduce heat loss in a shed made mostly of concrete blocks.

Answer 2

• Close doors & windows
• Use cladding
• Use double thickness of concrete
• Use silver/ reflective/ white paint
• Plant more trees around wind break
• Double glaze windows

Question 3

More water is added to a tank.

Explain how the pressure on the bottom of the tank changes when more water is added.

Answer 3

• Greater pressure
• Force at the bottom of the tank is greater due to water

Question 4

Suggest one reason why atmospheric pressure is greater at 2000 m than at 6000 m above sea level.

Answer 4

• Greater density of atmosphere
• Greater depth of atmosphere
• Greater temperature of atmosphere

Question 5

Two magnets are held the same distance apart but with the N-pole of one magnet facing the S-pole of the other magnet. The value of constant K does not change.

State how the force would compare with the force, when the magnets are held with their N-poles facing each other.

Answer 5

Opposite direction and same magnitude

Question 6

Explain why the total amount of work done by a cyclist traveling uphill is different than the change in gravitational potential energy of the cyclist traveling uphill, assuming the distances are equal.

Answer 6

• Some work is done to overcome friction/ air resistance
• Energy is dissipated/ transferred to the environment

Question 7

State how the overall resistance changes when any one of the devices is switched off in a parallel circuit.

Answer 7

Overall resistance increases

Question 8

Explain how an alternating current in a primary coil causes an alternating current in the secondary coil of a transformer.

Answer 8

• An alternating magnetic field is generated when an alternating potential difference/ voltage is applied across the primary coil
• The alternating magnetic field links the secondary coil
• The alternating magnetic field induces an alternating voltage across the secondary coil

Question 9

A student investigates the forces between some trucks in a wooden toy railway. She places another truck, A, next to truck B. She pulls the engine in one direction and the whole train travels at a constant speed.

The student repeats this method of adding trucks and pulling the train each time. When there are seven trucks in total, the train comes apart between the engine when tested.

Explain why the train acts in this way by considering the forces involved.

Answer 9

• Frictional forces increase as more trucks are added
• In order to keep constant speed, the student must increase the force she applies to the engine
• When the engine and truck B separate, the frictional forces to the left are more than the magnetic attraction between the engine and truck B

Question 10

A student investigates the forces between some trucks in a wooden toy railway. She places another truck, A, next to truck B. She pulls the engine in one direction and the whole train travels at a constant speed.

The student repeats this method of adding trucks and pulling the train each time. When there are seven trucks in total, the train comes apart between the engine when tested.

Devise an experiment to investigate the horizontal force needed to separate the trucks from the engine.

Answer 10

• Use a Newtonmeter horizontally
• Record largest force observed
• Repeat readings several times to avoid anomalies

Question 11

A student investigates the forces between some trucks in a wooden toy railway. She places another truck, A, next to truck B. She pulls the engine in one direction and the whole train travels at a constant speed.

The student repeats this method of adding trucks and pulling the train each time. When there are seven trucks in total, the train comes apart between the engine when tested.

Explain why a larger force is needed to separate the trucks from the engine if the force is applied at an angle to the horizontal.

Answer 11

• The applied force must be resolved horizontally to determine the force that separates the engine from the trucks
• Since the size of the resolved force is always smaller than the actual force, a larger force is needed

Question 12

A power transmission wire hangs so that it is at right angles to the Earth’s magnetic field. Although this magnetic field is constant, the cable experiences a changing force.

Explain why the force experienced by the cable changes.

Answer 12

• The transmission wire carries an alternating current
• The force caused by this current varies in size and direction
• The direction of the force depends on the direction of the current and therefore changes direction
• The magnitude of the force depends on the magnitude of the current and therefore changes magnitude

Question 13

When the handle of a small generator is turned, the current produced lights a lamp.

Describe what happens inside the generator to produce this current.

Answer 13

The magnet near/ close to the coil spins/ rotates

Question 14

What is a system?

Answer 14

A single object/ group of objects

Question 15

Give three ways that the energy of a system can be changed.

Answer 15

• Mechanical work - a force moving an object through a distance
• Electrical work - charges moving due to a potential difference
• Heating - due to temperature difference caused electrically or by chemical reaction
• Radiation - energy transferred as a wave(eg. light and infrared - light radiation and infrared radiation are emitted from the sun)

Question 16

Define power. State the equation relating power, work done and time.

Answer 16

• Rate of energy transfer
• Power = Work Done/ Time

Question 17

What force causes the repulsion of two like electrical charges? What causes this force?

Answer 17

• Electrostatic force
• Interacting magnetic fields

Question 18

What is an interaction pair?

Answer 18

Two objects exerting an equal but opposite force on each other (Newton’s 3rd Law)

Question 19

What is meant by the resultant force acting on an object?

Answer 19

• Overall/ Net force on a point/ object

Question 20

Briefly explain why resistance increases with temperature for a resistor.

Answer 20

• Work is done against resistance when an electrical charge flows through a component
• Causes an electrical transfer of energy
• Some of this energy is transferred usefully but some are dissipated to the thermal energy stores of the component and its surroundings
• When a current flows through a resistor, the resistor heats up

Question 21

Explain how you would investigate how the current through a component affected its resistance.

Answer 21

• Connect ammeter in series and voltmeter in parallel to a resistance wire
• Connect crocodile chips to resistance wire
• Increase current at regular intervals
• Record results from the ammeter and voltmeter and repeat readings to avoid anomalies
• Using the equation Resistance = Voltage/ Current, work out the resistance
• Record results in a table and likewise plot a resistance - current graph

Question 22

What happens to the resistance of a thermistor as it gets hotter?

Answer 22

Resistance decreases

Question 23

How does the current through each component vary in a series circuit?

Answer 23

• Size of current depends on total potential difference/ voltage and total resistance
• Current is same everywhere

Question 24

Give the potential differences for the three wires in a three-core mains cable.

Answer 24

• Live wire - 230 V
• Earth wire - 0 V
• Neutral wire - 0 V

Question 25

Describe the magnetic field around a current-carrying wire.

Answer 25

• The field is made up of concentric circles perpendicular to the wire, with the wire at center
• Changing the direction of the current changes the direction of the magnetic field
• The larger the current through the wire / closer you are to the wire, the stronger the magnetic field (field lines are closer to one another)

Question 26

Explain why a current-carrying conductor experiences a force.

Answer 26

• Current is put between magnetic poles and two magnetic fields interact
• A full force is experienced when wire is at right angles to the magnetic field

Question 27

What is Fleming’s Left Hand Rule?

Answer 27

• Thumb, first and second finger are held mutually perpendicular from each other
• The first finger equals the direction of the magnetic field
• The second finger equals the direction of the current
• The thumb equals the direction of the force

Question 28

Explain the shape and strength of the magnetic inside and outside a solenoid.

Answer 28

• Magnetic field lines point to the same direction and magnetic field strength is almost uniform inside a solenoid
• Magnetic field lines overlap and the strength is weaker apart from the ends/ poles outside the solenoid

Question 29

True or false? Induced currents create magnetic fields that oppose the charge the change that made them?

Answer 29

True

Question 30

Define gas pressure for a sealed container.

Answer 30

Collisions between gas particles causing a net force acting outwards on the inside surface of a container

Question 31

Explain why you need more than one force acting on an object to cause it to stretch.

Answer 31

The object would simply move in the direction of the applied force otherwise instead of changing shape

Question 32

Give one reason why the reduction in length of a spring eventually reaches a limit as more weights are added.

Answer 32

Coils are pushed together/ Spring is fully compressed

Question 33

Comment on the relationship between the overall resistance of a circuit and the no. of resistors in parallel.

Answer 33

• Overall resistance decreases as the no. of resistors increases in a parallel circuit
• Non-linear
• Inversely proportional

Question 34

A wooden block on a table is connected to a weight by a string. The string goes over a pulley. The surfaces of the table and the wooden block are both rough. The wooden block moves across the table at a constant horizontal velocity. Several vertical and horizontal forces act on the wooden block as it moves.

Explain how the forces keep the wooden block moving across the table at a constant velocity, via referring to all forces acting on the wooden block.

Answer 34

• Tension in string
• Tension is one of the horizontal forces acting on the wooden block
• Friction between table and wooden block
• Friction acts in opposite direction to tension
• Friction opposes motion
• Horizontal forces are equal and opposite
• Wooden block is in equilibrium/ no resultant force, therefore moves at constant velocity
• Normal reaction force upwards between table and wooden block
• Contact force
• Weight of block downwards
• Weight and normal reaction force are equal and opposite
• Wooden block doesn’t move up or down
• Tension caused by force due to gravity on weight
• Vertical forces acting on wooden block do not affect horizontal velocity

Question 35

A toy has a plastic cylinder, a plastic base and two similar magnets. Each of the two magnets is in the shape of a ring. The upper magnet seems to float in the air above the lower magnet.

Describe the forces acting on the upper magnet, via using the idea of magnetic fields.

Answer 35

• Magnetic fields interact
• Due to repulsion between magnets
• Repulsion force acts upwards on the upper magnet
• Weight/ Gravitational force acts downwards on the upper magnet
• Forces are equal/ in equilibrium

Question 36

An electrical device is connected to the wheels of an electric car. The electrical device is used as a motor when the car accelerates and as a dynamo when the car decelerates.

Explain how using the device can help to increase the time that the car can be driven before the battery becomes discharged.

Answer 36

Energy is transferred from kinetic to chemical energy store

Question 37

A pulley system enables a person to lift a heavy barrel. The person pulls down on the rope to make the barrel rise. Some energy is wasted due to friction.

Suggest another reason why some energy is wasted in using this pulley system.

Answer 37

• Additional mass in the system
• Energy is used to stretch the rope