Explain the following : (a) Why is tungsten used almost exclusively for filament of electric lamps? (b) Why are the conductors of electric heating devices, such as breadtoasters and electric irons, made of an alloy rather than a pure metal? (c) Why is the series arrangement not used for domestic circuits? (d) How does the resistance of a wire vary with its area of cross-section? (e) Why are copper and aluminium wires usually employed for electricity transmission?

An electric heater of resistance 8 W draws 15 A from the service mains for 2 hours. Calculate the rate at which heat is developed in the heater.

Which uses more energy, a 250 W TV set in 1 hr, or a 1200 W toaster in 10 minutes?

Two lamps, one rated 100 W at 220 V, and the other 60 W at 220 V, are connected in parallel to the electric mains supply. What current is drawn from the line if the supply voltage is 220 V?

Compare the power used in the 2 Ω resistor in each of the following circuits: (i) A 6 V battery in series with 1 Ω and 2 Ω resistors. (ii) A 4 V battery in parallel with 12 Ω and 2 Ω resistors.

A hot plate of an electric oven connected to a 220 V line has two resistance coils A and B, each of 24 Ω resistance, which may be used separately, in series, or parallel. What are the currents in the three cases?