Question

A current of 1 A is drawn by a filament of an electric bulb. Number of electrons passing through a cross section of the filament in 16 seconds would be roughly:

• A. ${10}^{20}$
• B. ${10}^{16}$
• C. ${10}^{18}$
• D. ${10}^{23}$

Answer 1

Answer: (A)

$\text{Given :}I=1A,t=16s,e=1.6\times {10}^{-19}C$

$\text{Step 1: Current drawn by the filament}$

$I=\frac{Q}{t}=\frac{Ne}{t}$ (Since $Q=Ne$, where N is the number of electrons crossing in time t)

$\Rightarrow N=\frac{It}{e}$ $....\left(1\right)$

$\text{Step 2: Substituting the values in equation (1)}$

$N=\frac{It}{e}=\frac{1A\times 16s}{1.6\times {10}^{-19}C}={10}^{20}$

Hence, number of electrons passing through a cross section of the filament in 16 seconds would be ${10}^{20}$.