Question

If an electron is moving in a magnetic field of $5.4\times {10}^{-4}T$ on a circular path of radius 32 cm having a frequency of 2.5 MHz, then its speed will be

• A. $8.56\times {10}^{6}m{s}^{-1}$
• B. $5.024\times {10}^{6}m{s}^{-1}$
• C. $8.56\times {10}^{4}m{s}^{-1}$
• D. $5.024\times {10}^{4}m{s}^{-1}$

Answer 1

Answer: (B)

$5.024\times {10}^{6}m{s}^{-1}$

Here, $B=5.4\times {10}^{-4}T;$
$r=32cm=32\times {10}^{-2}m,v=2.5MHz=2.5\times {10}^{6}Hz$
The speed of electron on circular path
$v=r\times 2\pi v=32\times {10}^{-2}\times 2\times 3.14\times 2.5\times {10}^6$
$=502.4\times {10}^4=5.024\times {10}^{6}m{s}^{-1}$