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What is the meaning of the symbol kWh? Which quantity does it represent?
An electric heater is rated at 2 kW. Electrical energy costs Rs 4 per kWh. What is the cost of using the heater for 3 hours?
(a) Rs 12
(b) Rs 24
(c) Rs 36
(d) Rs 48
The table below shows the current in three different electrical appliances when connected to the 240 V mains supply:
| Appliance | Current |
| Kettle | 8.5 A |
| Lamp | 0.4 A |
| toaster | 4.8 A |
- Which appliance has the greatest electrical resistance? How does the data show this?
- The lamp is connected to the main supply by using a thin, twin-cored cable consisting of live and natural wires. State two reasons why this cable should not be used for connecting the kettle to the mains supply.
- Calculate the power rating of the kettle when it is operated from the 240 V mains supply.
- A main takes the kettle abroad where the mains supply is 120 V. What is the current is the kettle when it is operated from the 120 V supply?
A bulb of 40 W is used for 12.5 h each day for 30 days. Calculate the electrical energy consumed.
State the S.I. units of electrical power and electrical energy.
(i) Define the household unit of electricity.
(ii) What is the voltage of the electricity that is generally supplied to a house?
An electric bulb of resistance 500 Ω draws current 0.4 A from the source. Calculate:
- the power of bulb and
- the potential difference at its end.
What is the order of current drawn by appliances connected to the ‘light circuit’ of a household?
An electric bulb is rated as 100W – 250V. What information does it convey? Calculate the current through the filament of the bulb.
The resistance of filament of an electric heater is 500 Ω It is operated at 200V for 1 hour daily. Calculate the current drawn by the heater and the energy consumed in kWh, by the heater in a month of 30 days.
1 kWh is equal to:
