An electric iron of resistance 20 `Omega` takes a current of 5 A. Calculate the heat developed in 30 s.

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

An electric lamp, whose resistance is 20 Omega , and a conductor of 4 Omega resistance are connected to a 6 V battery (Fig. 12.9). Calculate (a) the total resistance of the circuit, (b) the current through the circuit, and (c) the potential difference across the electric lamp and conductor.

An electrical meter of internal resistance 20Omega gives a full scale deflection when one milliampere current flows through it. The maximum current, that can be measured by using three resistors of resistance 12Omega each, in milliamperes is :

An electric lamp of 100 Omega , a toaster of resistance 500 Omega , and a water filter of resistance 500 Ω are connected in parallel to a 220 V source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances, and what is the current through it?