Question

A long straight wire carries a current of $10A$. An electron travels with a velocity of $5\times {10}^{6}m/s$ parallel to the wire $0.1m$ from it, and in a direction opposite to the current. The force does the magnetic field of current exert on the electron is :

• A. $1.6\times {10}^{-19}N$
• B. $3.2\times {10}^{-17}N$
• C. $1.6\times {10}^{-17}N$
• D. $3.2\times {10}^{-19}N$

Answer 1

The correct option is C $1.6\times {10}^{-17}N$

magnetic field due to straight wire =$\frac{{\mu }_{0}i}{2\pi r}$

|B| at $0.1m$ from wire =$\frac{2\times {10}_{-7}\times 10}{0.1}$ =$2\times {10}^{-5}T$

force for electron$=evB$
=$1.6\times {10}^{-19}\times 5\times {10}^6\times 2\times {10}^{-5}$
=$1.6\times {10}^{-17}N$