A metal wire of linear mass density of `9.8g//m` is stretched with a tension of `10 kg-wt` between two rigid support `1meter` apart. The wire passes at its middle point between the poles of a permanent magnet, and it vibrates in resonance when carrying an alternating current of frequency `n`. the frequency `n` of the alternating source is

Options

A. 100 Hz
B. 50 Hz
C. 25 Hz
D. 200 Hz

Answer

B

Explanation

At resonace, the frequency of a.c.
= Frequency of the vibrating wire (n)
` :. N = 1/(2 L) sqrt(T/m) `
` = 1/(2 xx 1) sqrt((10 xx 9.8)/( 9 .8 xx 10^(-3)))`
` = 1/2 sqrt(10^(4)) = 100/ 2 = 50` hz