Question

(a) Define electirc current. What is the SI unit of electric current.
(b) One coulomb of charge flows through any cross-section of a conductor in 1 second. What is the current flowing through the conductor?
(c) Which instrument is used to measure electric current ? How should it be connected in a circuit?
(d) What is the conventional direction of the flow of electric current ? How does it differ from te direction of flow of electron?
(e) A flash of lightning carries 10 C of charge which flows for 0.01 s. What is the current? If the voltage is 10 MV, What is the energy?

Answer 1

a) Electric current is defined as the rate of flow of electric charge through any cross-section of a conductor. The SI unit of electric current is ampere (A).

b) Current, $I=\frac{Q}{t}=\frac{1C}{1s}=1A$

c) The instrument used to measure current is called an ammeter and is connected in series in the circuit

d) Conventional direction of flow of electric current is from positive to negative terminal of the battery in the external circuit. The direction of flow of electrons is opposite to the conventional direction of flow of current.

e) $I=\frac{Q}{t}=\frac{10C}{0.01s}=1000A$

$W=VQ=10\times {10}^6\times 10=100\times {10}^{6}J=100MJ$