ELECTRICAL POWER AND HOUSEHOLD CIRCUITS
2015
1. i) Name the device used to increase the voltage at a generating station.
ii) At what frequency is a.c. supplied to residential houses?
iii) Name the wire in a household electrical circuit to which the switch is connected. [3]
2014
1. i) Two sets A and B, of three bulbs each, are glowing in two separate rooms. When one of the bulbs in set A is fused, the
other two bulbs also cease to glow. But in set B, when one bulb fuses, the other two bulbs continue to glow. Explain why
this occurs. Ii) Why do we prefer arrangement of set B for house circuiting? [3]
2013 i) An electrical gadget can give an electric shock to its user under certain circumstances. Mention any two of these
circumstances.
ii) What preventive measure provided in a gadget can protect a person from an electric shock? [3]
2012
1. i) Write an expression for the electrical energy spent in the flow of current through an electrical appliance in terms of I, r and
t.
ii) At what voltage is the alternating current supplied to our houses?
iii) How should the electric lamps in a building be connected? [3]
2010
1. i) Which part of an electrical appliance is earthed?
ii) State the relation between electrical power, resistance and potential difference in an electrical circuit. [2]
2. Calculate the quantity of heat that will be produced in a coil of resistance 75 if a current of 2 A is passed through it for 2
minutes. [3]
2009
1. The diagrams (a) and (b) given below are of a plug and socket with
arrows marked as 1,2,3 and 4,5,6 respectively on them. Identify and
write Live (L), Neutral (N) and Earth (E) against the correct number.
2008
1. Draw a labelled diagram of the staircase wiring for a dual control switch showing a bulb in the circuit.
2. The electrical gadgets used in a house such as bulbs, fans, heater, etc, are always connected in parallel not in series. Give
two reasons for connecting them in parallel.
3. An electrical heater is rated 4kW, 220 V. Find the cost of using this heater for 12 hours if one kWh of electrical energy costs
Rs. 3.25.
2007
1. Define kilowatt hour. How is it related to joule?
2. Of the three connecting wires in a household circuit: i) which two of the three wires are at the same potential? ii) in which of
the three wires should the switch be connected?
3. What is meant by earthing of an electrical appliance? Why is it essential?
4. What will be the effect on the working of an electric bell is instead of a direct current, an alternating current is used?
2006
1. Draw a labeled diagram of a three-pin socket.
2. Find the cost of operating an electric toaster for two hours if it draws 8A current on a 110 V circuit. The cost of electrical
energy is Rs. 2.50 per kWh.
2005
1. In a three-pin plug, why is the earth pin made longer and thicker than the other two pins?
2. An electrical appliance is rated 1500W, 250 V. This appliance is connected to 250V mains. Calculate: i) the current drawn
ii) the electrical energy consumed in 60 hours. iii) the cost of electrical energy consumed at Rs. 2.50 per kWh.
2004
1. State the purpose of a fuse in an electric circuit. Name the material used for making a fuse wire.
2003
1. What is the voltage of the electricity that is generally supplied to a house?
2. Which of the two wires of similar dimensions, copper or nichrome, would you use for the electric heater element? Give
reasons to justify your answer.
3. Two fuse wires of the same length are rated 5A and 20A. Which of the two fuse wires is thicker and why?
4. An electric kettle is rated 2.5 kW, 250V. Find the cost of running the kettle for two hours at 60 paise per unit.
2002
1. A geyser has a label 2 kW, 240 V. What is the cost of using it for 30 minutes, if the cost of electricity is Rs. 3 per
commercial unit?
2. Explain briefly the function of the following in the household wiring: i) a three-pin plug ii) main switch.
3. Make a table with the names of three electrical appliances used in your home in one column, their power, voltage rating and
the approximate time for which one is used in one day in the other columns.
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