Question

An electron is moving in a circular path of radius $5.1\times {10}^{-11}$ m at a frequency of $6.8\times {10}^{15}$ revolutions/sec. The equivalent current is approximately equal to _______.

• A. $5.1\times {10}^{-3}A$
• B. $6.8\times {10}^{-3}A$
• C. $1.1\times {10}^{-3}A$
• D. $2.2\times {10}^{-3}A$

Answer 1

The correct option is C $1.1\times {10}^{-3}A$

Given:
Frequency, $f=6.8\times {10}^{15}rev/s$,

Charge of electron, e = $1.6\times {10}^{-19}C$

So we can write
Time Period, $T=\frac{1}{frequency}=\frac{1}{6.8\times {10}^{15}}s$

We know,
Current is given by:

$I=\frac{Q}{T}=\frac{e}{T}=e\times f$

Putting all the values

$I=1.6\times {10}^{-19}\times 6.8\times {10}^{15}$

After solving

$I=1.1\times {10}^{-3}A$

Hence the correct option is (B)