Topic 2

High Demand Questions QUESTIONSHEET 1

Here is a diagram of an electric bell.

Explain how the bell works by referring to the parts labelled A – E.

(7)

................................................................................................................................................................

............................................................................................................................................................ [7]

TOTAL / 7

High Demand Questions QUESTIONSHEET 2

(a) A large electromagnet is used in a scrap yard to move old cars.

(i) Name a suitable material for the electromagnet.

(1)

............................................................................................................................................................ [1]

(ii) Explain your choice.

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(b) A car of mass 1600 kg can be just be lifted.

What is the least force that the electromagnet must use to lift the car?

(1 g = 10 N/kg)

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

TOTAL / 5

High Demand Questions QUESTIONSHEET 3

Describe a simple electric motor.

Include a simple diagram in your answer.

(7)

................................................................................................................................................................

[7]

TOTAL / 7

High Demand Questions QUESTIONSHEET 4

(a) An electric motor is connected to the external circuit via a split ring commutator.

pivot

coil

Explain the purpose of this.

(3)

................................................................................................................................................................

............................................................................................................................................................ [3]

(b) (i) How could the motor be used as a generator ?

(1)

............................................................................................................................................................ [1]

(ii) The current produced would be a varying direct current (dc).

What changes would be needed for the generator to produce an alternating current (ac) instead ?

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

TOTAL / 6

High Demand Questions QUESTIONSHEET 5

(a) The diagram shows a relay circuit used in a car starter motor.

starter motor

What happens when the ignition is switched on ?

................................................................................................................................................................

............................................................................................................................................................ [3]

(b)Why is the battery always connected to the starter motor with very thick cables ?

(1)

............................................................................................................................................................ [1]

(c)Draw a circuit diagram showing the battery connections.

[3]

TOTAL / 7

High Demand Questions QUESTIONSHEET 6

(a) The diagram below shows a device that could be used for measuring the rate at which water flows through a

pipe.

Explain why a reading is obtained on the meter when the water flows in the pipe.

(4)

................................................................................................................................................................

............................................................................................................................................................ [4]

(b) State the effect on the meter of

(i) increasing the flow rate of the water

(1)

............................................................................................................................................................ [1]

(ii) making the water flow in the opposite direction

(1)

............................................................................................................................................................ [1]

TOTAL / 6

High Demand Questions QUESTIONSHEET 7

(a) To avoid cutting through cables, a gas company uses a device to detect their position before digging holes.

The magnetic field produced by the cable induces a voltage across the coil. This is registered on a meter attached to the device.

The device cannot detect cables that carry a steady direct current. Explain the reason for this.

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(b)Why is it better to use the coil vertically than horizontally?

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(c)State two ways in which you could get a larger reading on the meter.

1. ........................................................................................................................................................ [1] .................................................................................................................................................................. ............................................................................................................................................................ (1)

TOTAL / 6

High Demand Questions QUESTIONSHEET 8

(a) The heating effect of an electric current is given by

H = I²R

where I = current, R = resistance.

If the power generated from a power station is 150 kW at a voltage of 275 kV, calculate the current in

the cable.

(4)

................................................................................................................................................................

............................................................................................................................................................ [4]

(b) (i) The resistance of the cable is 0.01 W per km.

Calculate the total resistance of a 200 km length of the cable.

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(ii) Find the power loss in the cable over 200 km.

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

TOTAL / 8

Medium Demand Questions QUESTIONSHEET 9

(a) A wire is positioned between two magnets. The wire is connected to a battery.

Describe what happens.

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(b) (i) The connections are reversed.

Describe what happens now.

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(ii) The battery is replaced by a power supply that gives an alternating current.

What is observed ?

(1)

............................................................................................................................................................ [1]

TOTAL / 5

Medium Demand Questions QUESTIONSHEET 10

(a) Chloe makes an electromagnet by coiling a length of wire around a pencil. What must she do to make it work ?

(1)

............................................................................................................................................................ [1]

(b) (i) Chloe is given some paper clips and asked to test the strength of her electromagnet.

How could she do this ?

................................................................................................................................................................

............................................................................................................................................................ [2]

(ii) State two ways in which Chloe could increase the strength of her electromagnet.

2. ........................................................................................................................................................ [1] .................................................................................................................................................................. .................................................................................................................................................................. (1)

TOTAL / 5

Medium Demand Questions QUESTIONSHEET 11

(a) A coil of wire is attached to a battery. An electric current flows through it.

The coil acts like a bar magnet.

Draw the magnetic field pattern around it. [2] (2)

(b) (i) A compass needle held near to the left-hand end points away from the coil.

What does this tell you ?

............................................................................................................................................................ [1] [1]

(ii) Show the direction of the magnetic field lines on your diagram. [1] (1)

TOTAL / 4

Medium Demand Questions QUESTIONSHEET 12

simple d.c. motor

(a) A simplified electric motor consists of a coil of wire connected to a battery and positioned between two

magnets (see diagram).

coil

brush (fixed)

brush

(fixed)

commutator

(rotates with coil)

(i) Use Fleming’s left-hand rule to predict the direction of the force on each arm of the coil.

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(ii) State the direction of motion of the coil.

(1)

............................................................................................................................................................ [1]

(b) (i) After half a turn the coil will stop.

What piece if equipment do you need to use to keep the coil moving ?

(1)

............................................................................................................................................................ [1]

(ii) What does the piece of apparatus do ?

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

TOTAL / 6

Medium Demand Questions QUESTIONSHEET 13

(a) The diagram shows a coil of wire connected to a sensitive ammeter. A bar magnet is moved towards the coil.

sensitive meter

S

What is observed on the ammeter?

(1)

............................................................................................................................................................ [1]

(b) What is observed if:

(i) the magnet is removed from the coil?

(1)

............................................................................................................................................................ [1]

(ii) the magnet and coil move in the same direction at the same speed?

(1)

............................................................................................................................................................ [1]

(1)

............................................................................................................................................................ [1]

(ii) State three factors which determine the size of the current produced.

1. ........................................................................................................................................................ [1]

2. ........................................................................................................................................................ [1]

3. ........................................................................................................................................................ [1] .................................................................................................................................................................. .................................................................................................................................................................. (3)

TOTAL / 7

Medium Demand Questions QUESTIONSHEET 14

(a) Some bicycles are fitted with a dynamo.

What is the purpose of a dynamo ?

............................................................................................................................................................ [1]

(b) It is not a good idea to have only lights which are powered by a dynamo.

Why not ?

................................................................................................................................................................

(i) How does this differ from a simple ac generator ?

................................................................................................................................................................

............................................................................................................................................................ [1]

(ii) What advantage does the dynamo arrangement have ?

................................................................................................................................................................

............................................................................................................................................................ [2]

TOTAL / 6

Medium Demand Questions QUESTIONSHEET 15

(a) The National Grid is made up of a network of cables transmitting electricity from power stations

across the country.

A typical power station generates electricity at 25000 V.

The electricity is actually transmitted at 400 000 V.

(i) How is this achieved ?

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(ii) Why is this done ?

(3)

................................................................................................................................................................

............................................................................................................................................................ [3]

(b) (i) Why might you see a notice warning that it is dangerous to fly kites near to overhead voltage cables ?

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(ii) Why is it safe for a bird to perch on an overhead voltage cable ?

(3)

................................................................................................................................................................

............................................................................................................................................................ [2]

TOTAL / 9

Medium Demand Questions QUESTIONSHEET 16

(a)From what material is the core of a transformer made ?

(1)

............................................................................................................................................................ [1]

(b) What is the purpose of the core ?

(1)

............................................................................................................................................................ [1]

Explain why.

(3)

................................................................................................................................................................

............................................................................................................................................................ [3]

TOTAL / 5

Low Demand Questions QUESTIONSHEET 17

(a) A wire is connected to a low voltage supply. A current flows as shown and a magnetic field is produced.

Direction of current

Low

voltage

supply

State two ways in which the magnetic field could be detected.

1. ............................................................................................................................................................

............................................................................................................................................................ [2] .................................................................................................................................................................. .................................................................................................................................................................. (2)

2. ............................................................................................................................................................

(b)Make a sketch of the magnetic field pattern.

Show the direction of the magnetic field. (2)

[2]

TOTAL / 6

Low Demand Questions QUESTIONSHEET 18

(a) What is meant by an alternating current ?

(2)

................................................................................................................................................................

............................................................................................................................................................ [2]

(b)Which of the following graphs show an alternating current ?

time

time

............................................................................................................................................................ [2] .................................................................................................................................................. (one line) .................................................................................................................................................................. ............................................................................................................................................................ (2)

TOTAL / 4

Low Demand Questions QUESTIONSHEET 19

Below is a block diagram of a fossil fuel power station.

(a)(i) What is meant by a fossil fuel?

............................................................................................................................................................ [1]

(ii) Name two commonly used fossil fuels

................................................................................................................................................................

............................................................................................................................................................ [2]

(b) Explain how the power station works

................................................................................................................................................................

............................................................................................................................................................ [6]

TOTAL / 9

Low Demand Questions QUESTIONSHEET 20

(a) Name three machines, which make use of motors.

................................................................................................................................................................

............................................................................................................................................................ [3]

(b) Electric motors make use of carbon brushes.

What two properties of carbon make it a good material to use?

................................................................................................................................................................

............................................................................................................................................................ [2]

................................................................................................................................................................

............................................................................................................................................................ [2]

TOTAL / 7