Question

Define electric current. A current of 1A is drawn by a filament of an electric bulb for 30 sec. Find the amount of electric charge that flows through the circuit.

Answer 1

Hint: A current refers to the flow of a substance. When a stream of charge flows in a wire it produces an electric current. That is, the charge flow per unit time is the electric current.

Complete step-by-step answer:
Electric current in a wire is defined as the amount of charge flow per unit time. Change is measured in coulombs, whereas time has the unit seconds. Therefore, the SI unit of current Ampere is basically:
$\text{Ampere}=\dfrac{\text{Coulomb}}{\text{Second}}$
When a potential difference is applied at two ends of a metallic wire, the free electrons start moving from higher to lower potential, producing an electric current in the opposite direction.
The rate of flow of electric charge is called electric current, mathematically it is
$I=\dfrac{q}{t}$
Where $I$,is the current in amperes. $q$ is the amount of charge flown in coulomb and $t$ is time taken in seconds.
Therefore, for a current of 1A flowing for 30 seconds, the amount of charge flow becomes:
$q=I\times t$
$q=1A\times 30\sec =30C$
Amount of charge flown is 30 coulombs.

NOTE: Firstly, students generally make mistakes in choosing the unit, when there is Ampere one should always convert time in seconds. Secondly, if you are unable to remember the formula of the charge flow in the circuit, you can guess it by using the units and arranging them in a fashion you get the unit of charge. That is, when current in Ampere (coulomb/sec) and time in seconds is given. Charge with the unit coulomb can be received by multiplying Ampere and seconds. That is, Charge is Current multiplied by Time.