Question

An electron enters a magnetic field of intensity 8T with a velocity $2\times {10}^{6}m/s$ in a direction at an angle of ${90}^{\circ }$ with the field. The force acting on the electron is

• A. $1.6\times {10}^{-12}N$
• B. $2.56\times {10}^{-12}N$
• C. $2.56\times {10}^{-14}N$
• D. $1.6\times {10}^{-14}N$

Answer 1

The correct option is B $2.56\times {10}^{-12}N$

Charge on electron, $q=–1.6\times {10}^{–19}C$
Magnetic field, B = 8T
Velocity of electron, $v=2\times {10}^{6}m/s$
Angle between magnetic field and velocity of electron, $\theta ={90}^{\circ }$
$\therefore$ Force acting on the electron, $\overline{F}=q\overline{v}\times \overline{B}$
$=1.6\times {10}^{-19}\times 2\times {10}^6\times 8\times sin{90}^{\circ }$
$=2.56\times {10}^{-12}N$
Hence, the correct answer is option (2).