Question

What is the charge on $\text{'}X\text{'}$, if a body $X$ loses $125\times {10}^{18}$ electrons by rubbing it with another body $\text{'}Y\text{'}$?

• A. $+20C$
• B. $+2C$
• C. $-8C$
• D. $-20C$

Answer 1

The correct option is A

$+20C$

Step 1:Given data

Number of electrons lost, $n=125\times {10}^{18}$
Charge on an electron, $e=-1.6\times {10}^{-19}\hspace{0.17em}C$

Step 2: Calculate the charge on body ‘X’

We know that by quantization of charge.

Charge is given by relation, $Q=ne$

Substituting the value of $n=125\times {10}^{18}$ and $e=-1.6\times {10}^{-19}\hspace{0.17em}C$

$$\begin{gathered} Q=ne \\ Q=(125\times {10}^{18})(-1.6\times {10}^{-19}) \\ Q=-125\times 1.6\times {10}^{-1} \\ Q=-20C \end{gathered}$$

This is the charge lost by the body. Since the body loses a negative charge it will gain the same amount of positive charge on it.

Hence, option (a)$+20C$ is correct.