Question

A metal wire of linear mass density of 9.8g/m is stretched with a tension of 10kgwt between two rigid supports 1metre 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 u. The frequency u of the alternating source is

(a) 50 Hz 

(b) 100 Hz

(c) 200 Hz 

(d) 25 Hz.

Answer 1

(a) : At resonance, the frequency of vibration of wire become equal to the frequency of a.c.