Changkat Changi Secondary School
Physics Department
Secondary 4 Express / 5 Normal Academic
Name: ______( ) Class: ______Date: ______
TOPIC : PRACTICAL ELECTRICITY
WORKSHEET 17.2
A. MULTIPLE CHOICE QUESTIONS (5 Marks)
1. A plug connected to a table lamp contains a 3 A fuse. Why is the fuse needed?
A To increase the resistance of the circuit
B To make it easier for the current to flow
C To protect the wiring from overwhelming
D To reduce the voltage across the lamp ( )
2. Which circuit shows the correct positions for the fuse and switch in the lightning circuit of a house?
( )
3. A student suggests setting up the electrical circuit shown in the diagram. Why is this circuit unsafe?
A The fuse is in the wrong supply lead.
B The fuse value is too small.
C The lamp has too small a voltage.
D The switch is in the wrong supply lead.
( )
4. Which fuse is the most appropriate for a 240 V, 1 kW heater?
A 3 A B 5 A C 10 A D 13 ( )
5. 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?
A 50 W B 250 W C 1000 W D 2000 W ( )
B. STRUCTURED QUESTIONS (30 Marks)
6. When an electric kettle is connected to a 240 V mains supply, a current of 6.0 A passes through it.
(a) When the kettle is operating normally, what current is flowing in
(i) the live wire, ______A [1]
(ii) the neutral wire, ______A [1]
(iii) the earth wire, ______A [1]
(b) Calculate the power supplied to the kettle. [2]
(c) Suggest a rating that could be used with this kettle. (Available: Fuses of 2 A, 5 A, 10 A, 13 A ratings) [1]
______
(d) Calculate the energy consumed by the kettle when it is switched on for 10 minutes. [2]
(e) Calculate the energy in kWh consumed by the kettle when it is switched on for 20 hours.
[2]
(f) The metal casing of the electric kettle is connected to the earth. Give one reason for this.
[2]
7. The following diagram shows the connections in a 13 A plug fitted to an electric kettle.
(a) State the colour (or colours) of the wire connected to each of the following terminals.
(i) Terminal A ______[1]
(ii) Terminal B ______[1]
(iii) Terminal C ______[1]
(b) Name part D. ______[1]
(c) What is the purpose of part D? [1]
______
(d) Which one of the terminal wires, A, B or C, is connected to the metal case of the kettle? [1]
______
(e) Explain why it is so important that the wire in answer (d) is connected to the metal case. [1]
______
8. A television set is rated at 800 W and operates on 250 V mains.
(a) Which fuse should you put in the plug? (2 A, 5 A or 13 A) [3]
(b) If the set was used for 10 hours, how many kilowatt-hours of electricity would be used? [2]
(c) If electricity costs 4 cents per kilowatt-hour, what is the cost of using the set for 10 hours?
[1]
9. A kettle is rated at 3 kW and works from a 240 V mains supply.
(a) Calculate the current taken by the kettle. [2]
(b) Explain why a 10 A fuse should not be used in the plug. [1]
______
______
(c) During a month, the kettle was used for 5 hours. How much did it cost to use the kettle if one unit (kWh) of electricity costs 20 cents? [2]
Worksheet 17.2 Page 4 of 4 Prepared by: Ms. Ng S R