question_answer

What is meant by electric circuit? Why does electric current start flowing in a circuit the moment circuit is complete? When do we say that the potential difference across a conductor in a circuit is 1 volt? Calculate the potential difference between the two terminals of a battery if 12 joules of work is done in transferring 2 coulombs of charge.

Answer:

(1) A continuous conducting path consisting of wires and other resistances (like electric bulb, etc.) and a switch, between the two terminals of a cell or a battery along which an electric current flows is called an electric circuit.

(2) It is the potential difference between the ends of the wire which makes the electric charges (or current) to flow in the wire.

(3) The potential difference between two points is said to be 1 volt if 1 joule of work is done in moving 1 coulomb of electric charge from one point to another.

Thus,    \[1\text{ volt=}\frac{1\text{ joule}}{1\text{ coulomb}}\]

Or         \[1V=\frac{1J}{1C}  or  1 J {{C}^{-1}}\]

Green    \[W=12\,J,    Q=2 C\]

Now,     \[V=\frac{W}{Q}=\frac{12J}{2\,C}=6\,volts\]