An electric iron rated 750 W is operated for 2 hours/day. How much energy is consumed by the electric iron for 30 days?
Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to electric mains supply. What current is drawn from the line if the supply voltage is 220 V?
Name the commercial unit of electric energy.
An electric lamp is labelled 12 V, 36 W. This indicates that it should be used with a 1 V supply. What other information does the label provide?
Define watt-hour. How many joules are equal to 1 watt-hour?
An electric bulb is connected to a 220 V power supply line. If the bulb draws a current of 0.5 A, calculate the power of the bulb.
Define kilowatt-hour.
At a given time, a house is supplied with 100 A at 220 V. How many 75 W, 220 V light bulb could be switched on in the house at the same time (if they are all connected in parallel)?
Name two gases which are filled in filament type electric light bulbs.
Which of the following is the most likely temperature of the filament of an electric light bulb when it is working on the normal 220 V supply line?
(a) 500°C
(b) 1500°C
(c) 2500°C
(d) 4500°C
Name the S.I. unit of electrical energy. How is it related to Wh?
Why is heating element wound on a long porcelain rod in a room heater.
Household wiring for lamp connections can either be done in parallel or in series.Which one would you prefer? Give a reason for your answer.
What changes in energy occur in an electric heater?
Why does not the heating coil produce any visible light? in an electric stove.
What is the order of current drawn by appliances connected to the ‘light circuit’ of a household?
Out of the three fuses with current ratings 5A, 10A, 15A, which one is to be connected in a geyser circuit marked 3 kW, 220V? Give reason for your answer.
A bulb is marked 100W, 220V and an electric heater is marked 2000 W, 220 V.
(i) What is the ratio between the resistances of these two devices?
(ii) How does the power-voltage rating of a device help us to decide about the type of leads (connecting wires) to be used for it?
(iii) In which of the above two devices, a thicker connecting wire of lead is required?
A family uses 8 kW of power. Direct solar energy is incident on the horizontal surface at an average rate of 200 W per square meter. If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW?
