17 Electricity 2021N

In which circuit is the ammeter measuring the flow of charge through the lamp?

In circuit 1, a negative charge flows in a clockwise direction. The bulb is bright.

In circuit 2, the battery is reversed as shown. The bulb is equally bright.

Which charge flows in circuit 2 and in which direction?

• negative, anticlockwise

• negative, clockwise

• positive, anticlockwise

• positive, clockwise

The diagram shows a circuit containing two resistors of resistance 1.0 Ω and 2.0 Ω.

A voltmeter is connected across the 1.0 Ω resistor by connecting P to X. The reading on the voltmeter is 6.0 V.

P is moved to point Y in the circuit.

What is the new reading on the voltmeter?

• 3.0 V

• 6.0 V

• 12 V

• 18 V

Which circuit contains a fuse?

Which row correctly shows the numbers of cells, lamps, and switches in the circuit?

• 1 | 1 | 4

• 1 | 4 | 1

• 3 | 1 | 4

• 3 | 4 | 1

The metal cases of electrical appliances are connected to an earth wire. Which statement is not correct?

• The live wire may become loose and touch the metal case.

• If the metal case becomes live, the earth wire conducts current to the ground.

• The earth wire needs to have a high resistance.

• Earthing metal cases helps prevent a person from receiving an electric shock.

A teacher asks, 'Why do we put a fuse in a mains circuit?'

Student 1 says, "it protects the wiring from overheating."

Student 2 says, "it protects us from getting a shock if we touch the live wire."

Who is correct?

• both students

• neither student

• student 1 only

• student 2 only

The current in a small electric heater is 4.0 A. The cable connected to the heater is able to carry currents up to 10 A. Fuses rated 1 A, 3 A, 5 A and 13 A are available.

Which fuse should be used?

• 1A

• 3A

• 5A

• 13A

Which circuit symbol represents a component used to measure electric current?

Four wires made of the same metal have different lengths and different diameters. Which wire has the lowest resistance?