6091 Physics Chapter 19 Practical Electricity

A 12 ohms resistor is connected across an 8.0 V supply as shown. What is the power produced in the resistor?

• 0.67 W
• 1.5 W
• 5.3 W
• 770 W

An electrical cable contains three wires: live, neutral and earth. The cable is correctly wired to a plug which contains a 3 A fuse. The insulation becomes damaged and bare metal wires show. Five possible events can occur. • A person touches the earth wire. • A person touches the neutral wire. • A person touches the live wire. • The live wire touches the neutral wire. • The live wire touches the earth wire.

How many of these five events cause the fuse in the plug to blow?

• 1
• 2
• 3
• 4

An electrical supply is used to light two lamps connected in parallel. What is the total current I ?

• 0.25 A
• 0.5 A
• 0.75 A
• 6.0 A

The circuits show a cell joined to different combinations of identical resistors. In which circuit is electrical energy transformed at the greatest rate?

• A
• B
• C
• D

A battery is used to light a 24 W electric lamp. The battery provides a charge of 120 C in 60 s. What is the potential difference across the lamp?

• 5 V
• 12 V
• 24 V
• 120 V

The potential difference (p.d.) between the ends of a conductor is 12 V How much electrical energy is converted to other forms of energy in the conductor when 100 C of charge flows through it?

• 0.12 J
• 8.3 J
• 88 J
• 1200 J

In a mains circuit, the switch of an electric heater is always wired into the live conductor. This is because, if the switch is wired into the neutral conductor,

• the circuit in the heater remains live when the switch is open.
• the fuse blows if the current is less than the fuse rating.
• the heater continues to operate when the switch is open.
• the heater does not operate when the switch is closed.

The diagram shows an old vacuum cleaner with plastic wheels and a metal case. The plug of the vacuum cleaner is wrongly wired as shown. What is the effect of using the plug wired this way?

• The fuse in the plug blows.
• The metal case becomes live.
• The vacuum cleaner catches fire
• The vacuum cleaner does not work.

It costs $0.30 for 1 kW h of electrical energy. How much will it cost to run a 60 W lamp for 10 hours?

• 0.05
• 0.18
• 3
• 18

The diagram shows the wiring of a mains electric lamp. The lamp has a metal case and a switch. There are three wires X, Y and Z in the mains cable connected to the plug. What is the correct arrangement of wires in the lamp?

• wire X = live, wire Y = earth, wire Z = neutral
• wire X = live, wire Y = neutral, wire Z =earth
• wire X = neutral, wire Y = earth, wire Z = live
• wire X = neutral, wire Y = live, wire Z = earth