With the help of a circuit diagram derive the formula for the resultant resistance of three resistances connected:
a) in series and
b) in parallel.

a) What is meant by electric current?
b) Name and define its unit.
c) Which instrument is used to measure the electric current? How should it be connected in a circuit?

a) State Joule’s law of heating.
b) An alloy of nickel and chromium is used as the heating element. Why?
c) How does a fuse wire protect electrical appliances?

Explain about domestic electric circuits. (circuit diagram not required)

a) What are the advantages of LED TV over the normal TV?
b) List the merits of LED bulb.

Two resistors when connected in parallel give the resultant resistance of 2 ohm; but when connected in series the effective resistance becomes 9 ohm. Calculate the value of each resistance.

How many electrons are passing per second in a circuit in which there is a current of 5 A?

A piece of wire of resistance 10 ohm is drawn out so that its length is increased to three times its original length. Calculate the new resistance.