Question

If 0.3A current is passed through a lamp, how many electrons will pass through it in 60s? $(e=1.6\times {{10}^{-19}}C)$
$\begin{aligned} & A.2.88\times {{10}^{20}} \\\ & B.1.125\times {{10}^{20}} \\\ & C.2.25\times {{10}^{20}} \\\ & D.1.8\times {{10}^{20}} \\\ \end{aligned}$

Answer 1

Here we have to use the relation between the current and the charge. From that we will get the amount of charge flowing in $60s$. Then we need to divide that amount of charge by the quantity of charge of one electron. Then we will get the desired answer. We will follow these steps here to solve the question.

Formula used:
$q=it,n=\dfrac{q}{e}$

Complete step by step solution:
The current is the amount of charge flowing in unit time. So If $i$ amount of current is flowing for $ts$ ,then the amount of charge flown in that time is given by
$q=it$ , now putting the values of all the quantities we get
$q=0.3\times 60=18C$ . Now the charge of one electron is $1.6\times {{10}^{-19}}C$ .So if $n$ number of electrons is there in $q$ amount of charge, we have
$n=\dfrac{q}{e}$ , Now putting the values of all the quantities we get
$n=\dfrac{18}{1.6\times {{10}^{-19}}}=1.125\times {{10}^{20}}$
Thus $1.125\times {{10}^{20}}$ number of electrons will pass through the bulb in $60s.$

Therefore, option (B) is the correct answer.

Additional information:
When some current flows through a conductor it opposes the movement of charges through it. This property of the conductor is called its resistance. Ohm’s law states that if there is no change in physical state of a conductor(such as temperature), then the ratio of the potential difference applied at its end and the current flowing through it is a constant and this constant is the resistance of the conductor.

Note:
To solve this kind of question we must take all the quantities in the same system of units.More the current more will be the number of electrons flowing in one second, because In any circuit electrons move from one part to another, so that we get current. The direction of the current is opposite to the direction of movement of electrons.