Question

Refer to the figure ,rectangle PQRS represents the cross section of a uniform magnetic field region of 0.20 T.An electron is projected at a speed of v=$2.0\times {10}^{6}m/s$ into the region at an angle of ${30}^0$ to the direction of the magnetic field .The length of the magnetic field region

• A. 28
• B. 16
• C. 9
• D. 32

Answer 1

Answer: (A)

28

Component of velocity perpendicular to magnetic filed is, $v_p=vsin{30}^0=1.0\times {10}^{6}m/s$

Thus radius for circular motion performed by electron under influence of magnetic field is,

$r=\frac{mv}{Be}=\frac{9.1\times {10}^{-31}\times {10}^6}{1.6\times {10}^{-19}\times 0.2}=28\mu m$