Electricity

The kWh is a unit of

• current

• energy

• power

• time

The diagram shows two resistors in parallel connected to a battery. The current from the battery is P and the currents through the resistors are Q and R.

What is the size of P?

• Q $\div$ R

• Q $-$ R

• Q $\times$ R

• Q + R

Diagram 1 shows two identical resistors R1 and R2 connected in series in a circuit. R2 is then removed as show in diagram 2.

• A

• B

• C

• D

A bulb in an electrical circuit has a current of 2A passing through it and a potential difference of 8V across it.

What is the power of the bulb?

• 0.016 kW

• 4 W

• 4 J

• 16 J

Which statement describes the behaviour of a battery?

• It delivers conventional current from the negative to the positive terminal.

• It delivers current when it is disconnected.

• It delivers current when it is connected to a resistor.

• It is made from two coils of wire would into a core of iron.

A television is fitted with a 3 A fuse and is connected to the 230 V mains supply. What is the purpose of the fuse?

• To break the circuit when the current is greater than 3 A

• To break the circuit when the mains supply is lower than 230 V

• To keep the current in the circuit at 3 A

• To keep the mains voltage at 230 V

The diagram shows a circuit.

The current at point P is 1.2 A. What is the current at point Q?

• 0.6 A

• 1.0 A

• 1.2 A

• 2.4 A

A circuit diagram contains the following symbol.

What does this symbol represent?

• a fixed resistor

• a fuse

• a switch

• a variable resistor

Electricity costs $0.20 per kWh. What is the cost of using a 0.5 kW heater for two hours?

• $0.20

• $0.50

• $50

• $200

A new electric saw has the following information displayed on the box:

1700 W

460 revolutions per minute

230 mm blade

6.9 kg

What is the power rating of the electric saw?

• 1700 W

• 460 revolutions per minute

• 230 mm

• 6.9 kg