17 Electricity 2023

Which statement about a voltmeter is correct?

• It has a scale which is marked in amperes (A).

• It must be connected in series in a circuit.

• It measures potential difference (p.d.).

• It must have three terminals.

How does the resistance of a metallic wire change: as its length increases as its cross-sectional area decreases?

Two 2.0Ω resistors are connected in parallel. What is the combined resistance of the resistors?

• less than 2.0Ω

• exactly 2.0Ω

• more than 2.0Ω, but less than 4.0Ω

• exactly 4.0Ω

An electric heater is plugged into the mains supply using a fused plug.

The current in the heater is 10 A.

The cable attached to the heater is rated at 15 A.

The fuses available are rated at 1.0 A, 3.0 A, 5.0 A and 13 A.

Which fuse should be used?

• 1.0 A

• 3.0 A

• 5.0 A

• 13 A

A battery is connected to an ammeter and a resistor. The ammeter reading is 0.20 A. An electrical insulator is connected in parallel with the resistor. What is the ammeter reading?

• 0 A

• between 0 A and 0.20 A

• 0.20 A

• greater than 0.20 A

Which unit is used to measure electromotive force (e.m.f.)?

• ampere

• joule

• volt

• watt

Which equation is correct for resistance R, potential difference (p.d.) V and current I?

• R = V/I

• R = V + I

• R = I/V

• R = V × I

In which heating system circuit would thermistors not be useful?

• to keep different rooms at different temperatures

• to turn an alarm on if the system overheats

• to turn a heating system off at a particular temperature

• to turn a heating system on when a sound is detected

Which statement is correct?

• A fuse is included in a circuit to prevent the current becoming too high.

• A fuse should be connected to the neutral wire in a plug.

• An electric circuit will only work if it includes a fuse.

• An earth wire is needed to prevent the fuse blowing.

Which graph of current I against time t represents an alternating current (a.c.)?