What happens when a 250 V, 2 500 W water heater is connected by a mains plug fitted with a 5A fuse?

1.   ?    The heater runs at a quarter power.
2.   ?    The heater runs at a half power.
3.   ?    The heater works normally.
4.   ?    The fuse in the plug blows.

The electric current in a resistor and the potential difference across the resistor are measured.
The readings are shown in the diagram.

1.   ?    0.10 W
2.   ?    0.75 W
3.   ?    0.90 W
4.   ?    9.0 W

A 3 kW electric fire has been used for 4 h at the cost of 5 cents per kW h.
What is the cost of the electrical energy used?

1.   ?    12 cents
2.   ?    15 cents
3.   ?    20 cents
4.   ?    60 cents

A plug connected to a table lamp contains a 3 A fuse.
Why is the fuse needed?

1.   ?    To make it easier for the current to flow
2.   ?    To increase the resistance of the circuit
3.   ?    To prevent the lamp from getting too bright
4.   ?    To protect the wiring from the overheating

A heater is to be used on a 250 W main circuit and has a 5 A fuse on its plug.
Which of the following is the most powerful heater that can be used safely with this fuse?

1.   ?    50 W
2.   ?    250 W
3.   ?    1 000 W
4.   ?    2 000 W

What is the formula to calculate electrical power?

1.   ?    Potential difference / Resistance
2.   ?    Potential difference / Current
3.   ?    Potential difference x Resistance
4.   ?    Potential difference x Current

While raising a load of 1 000 N, an electric motor runs with a steady input of 250 V and 4 A.
What is the time taken to lift the load vertically through a distance of 10 m?
(Assume 100% efficiency of the motor and transmission.)

1.   ?    1 s
2.   ?    1.5 s
3.   ?    4 s
4.   ?    10 s

How would the wires of a mains supply socket be connected if it is to be wired in parallel?

1.   ?    Live connected to neutral; Neutral to live; Earth to earth
2.   ?    Live connected to earth; Neutral to neutral; Earth to earth
3.   ?    Live connected to live; Neutral to earth; Earth to earth
4.   ?    Live connected to live; Neutral to neutral; Earth to earth

A small 2 watt electric motor is started by a dry-battery delivering 3 000 J to it.

How long after will the motor stop running when the battery is exhuasted?

1.   ?    25 minutes.
2.   ?    50 minutes.
3.   ?    100 minutes.
4.   ?    500 minutes.

Why is the filament of a light bulb made of tungsten in preference to copper?

1.   ?    Tungsten is cheaper and made more readily available.
2.   ?    Tungsten is more easily bent to the required shape.
3.   ?    Tungsten has a hight melting point.
4.   ?    Tungsten has a lower electrical resistance (resistivity).

The fuse for the lights of a house failed. When a new one is replaced, it failed again once the lighs are switched on. Another fuse is put in, this time, one with higher rating than the previous two.

This is not a sensible thing to do because .......................

1.   ?    a higher rating might worked but it would not correct the fault
2.   ?    higher rating fuse is already too high, that is why it failed
3.   ?    the rating id already too high, that is why it failed
4.   ?    fuses only work if the rating is exactly right

The diagram below shows four lamps being lighted up by a circuit.
One of the lamps if removed will cause all the light to go out.

1.   ?    A
2.   ?    B
3.   ?    C
4.   ?    D

The cost of electricity is 6p per kWh. If there is an immersion heater, a television and a number of lamps rated at 3 kW, what is the cost of using all those appliances for 4 hours?

1.   ?    4 x 3 x 60 x 6p
2.   ?    4 x 3 x 6p
3.   ?    ( 3 x 4 / 6 ) p
4.   ?    ( 3 x 6 / 4 ) p

Below is a diagram that shows the wiring from a 240 V mains supply to a socket outlet in a house.

1.   ?    1 and 5
2.   ?    2 and 4
3.   ?    1 and 3
4.   ?    2 and 3

Below is a diagram that shows a 240 V mains supply socket with a 750 W electric kettle attached to it by a flat-pin plug.

1.   ?    13 A in the neutal wire
2.   ?    13 A in the live wire
3.   ?    13 A in the earth wire
4.   ?    5 A in the live wire

Below is a diagram that shows an electrical mains supply connected to an electric heater be its three wires. The "live" wire has a current of 4 A flowing through it.

1.   ?    X: 4 A; Y: 0 A
2.   ?    X: 0 A; Y: 4 A
3.   ?    X: 4 A; Y: 4 A
4.   ?    X: 2 A; Y: 2 A

An ammeter is connected in the circuit as shown.

1.   ?    5 mA
2.   ?    20 mA
3.   ?    0.2 A
4.   ?    5 A

In the circuit shown, component Y can gradually change the brightness of the lamp.

1.   ?    a battery
2.   ?    a resistor
3.   ?    a switch
4.   ?    a variable resistor

A portable tape-recorder is rated at 12 W, 2 A.

How many 1.5 V batteries are needed in the tape-recorder?

1.   ?    3
2.   ?    4
3.   ?    6
4.   ?    8

A cell is connected in series with an ammeter and a lamp. The current is 1 A.

1.   ?    
2.   ?    
3.   ?    
4.   ?    

In each of the circuits below, a short circuit occurs.

In which circuit would the fuse blow and make the circuit safe to repair?

1.   ?    
2.   ?    
3.   ?    
4.   ?    

Which circuit will be the safest to use?

1.   ?    
2.   ?    
3.   ?    
4.   ?    

An electric plug often has three pins.

What is the longest pin connected to?

1.   ?    the earth wire
2.   ?    the fuse
3.   ?    the live wire
4.   ?    the neutral wire