Practical Electricity 1

A heater used on a 250 V mains circuit has a 5 A fuse in its plug.

Which is the highest power rating for this heater?
1. 50 W
2. 250 W
3. 1 000 W
4. 2 000 W
A plug is wrongly wired as shown. It is connected to an old vacuum cleaner which has a metal case.

What would be the effect of using the plug wired in this way?
1. The fuse in the plug would bow.
2. The metal case would be live.
3. The neutral wire would melt.
4. The vacuum cleaner would catch fire.
An electric lamp uses energy at the rate of 48 W with a 12 V supply.

How much charge passes through the lamp in 2.0 seconds?
1. 0.25 C
2. 0.50 C
3. 2.0 C
4. 8.0 C
Which circuit shows how the heater in an electric iron and a fuse should be connected to a mains electricity supply?
A student suggests setting up the electrical circuit shown in the diagram.

Why is the circuit unsafe?
1. The fuse is in the wrong supply lead.
2. The fuse value is too small.
3. The lamp has too small a wattage.
4. The switch is in the wrong supply lead.
A light bulb is marked 120 V, 60 W.
How much energy does one bulb dissipate in one minute?
1. 2 J
2. 60 J
3. 120 J
4. 3 600 J
An electric cooker is connected to the mains by a 3 core cable.
When the cooker is working correctly which wires carry the same current?
1. The live, the neutral and the earth.
2. The live and the earth.
3. The neutral and the earth.
4. The neutral and the live.
Which circuit shows the correct positions for the fuse and switch in the lightning circuit in the house?
1. A
2. B
3. C
4. D
A 2 kW electric fire is used for 5 hours.
How long will it take a 100 W electric light bulb to use the same amount of energy?
1. 400 hours
2. 100 hours
3. 50 hours
4. 20 hours
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
The kilowatt-hour is a unit of ................
1. charge.
2. energy.
3. power.
4. voltage.
An electrical appliance has a power of 1 000 W when operating from a 120 V supply.
Which fuse should be used with the appliance?
1. 3 A
2. 5 A
3. 10 A
4. 13 A
Which fuse is the most appropriate for a 240 V, 1 kW heater?
1. 3 A
2. 5 A
3. 10 A
4. 13 A
An electric kettle should always be fitted with an earth concentration for protection.
What is protected be the earth connection?
1. The cable connecting the kettle.
2. The fuse in the circuit.
3. The heating element of the kettle.
4. The person using the kettle.
A plug connected to a table lamp contains a 3 A fuse.
Why is the fuse needed?
1. To increase the resistance of the circuit
2. To make it easier for the current to flow
3. To protect the wiring form overheating
4. To reduce the voltage across the lamp
A torch bulb uses a 3 V supply and takes a current of 0.2 A. It is switched on for one minute.
How much electrical energy is used?
1. 0.6 J
2. 12 J
3. 36 J
4. 180 J
In order to turn off both wall lamps, which is the safest switch position?
1. A
2. B
3. C
4. D
A bulb rated 6 V, 2 A is switched on for 60 s.
How much energy is used?
1. 0.2 J
2. 20 J
3. 180 J
4. 720 J
A heater used on a 250 V mains circuit, has a 5 A fuse in its plug.
Which of the following is the most powerful heater that can be used with this fuse?
1. 50 W
2. 250 W
3. 1 000 W
4. 2 000 W
In an a.c. (household) electrical circuit, why should the switch for any device (such as an electric kettle) always be connected to the 'live' lead?
1. No current ever flows in the neutral lead of the device.
2. The device will be shorted if the switch is in the earth lead.
3. The device can never be switched off it the switch is the neutral lead.
4. The device can only be isolated (made safe) if the switch is in the live lead.
The earth wire of an electric appliance should be connected to the ..................
1. fuse
2. metal case
3. ON / OFF switch
4. plastic handle
Why is a fuse used in an electrical appliance?
1. To earth the appliance.
2. To protect the appliance.
3. To change the current rating of the appliance.
4. To change the voltage of the supply to the appliance.
A potential difference of 4 V drived a current of 3 A through a resistor.
How much electrical energy is converted into heat during 10 s?
1. 12 J
2. 30 J
3. 40 J
4. 120 J
The diagram shows some information printed on a light bulb.

What current is needed to light the bulb at normal brightness?
1. 0.1 A
2. 0.25 A
3. 3.0 A
4. 4.0 A
An electric heater takes 4 A of current from a 250 V supply when operating normally.
How long would it take the heater to convert 400 000 J of electrical energy?
1. 40 s
2. 400 s
3. 1 000 s
4. 1 600 s
Which of the following can be used to calculate electrical power?
1. Current x Resistance
2. Potential difference x Current
3. Potential difference x Resistance
4. Potential difference / Current

Practical Electricity 1

Multiple Choice Questions