Question

An infinitely long straight conductor carries a current of $5\, A$ as shown. An electron is moving with a speed of $10^{5} m / s$ parallel to the conductor. The perpendicular distance between the electron and the conductor is $20\, cm$ at an instant. Calculate the magnitude of the force experienced by the electron at that instant.

• A. $4 \times 10^{-20} N$
• B. $8 \pi \times 10^{-20} N$
• C. $4 \pi \times 10^{-20} N$
• D. $8 \times 10^{-20} N$

Answer 1

Answer: (D)

$B=\frac{\mu_{0} i^{i}}{2 \pi r}$
$F=e v B=\frac{e v \times \mu_{0} i}{2 \pi r}$
$=\frac{\left(1.6 \times 10^{-19}\right) \times 10^{5} \times 4 \pi \times 10^{-7} \times 5}{2 \pi \times 0.2} \,N$
$=\frac{1.6 \times 2 \times 5}{2} \times 10^{-20} \,N$
$\Rightarrow F=8 \times 10^{-20} \,N$