Question

In an a.c. generator the speed at which the coil rotates is doubled. How would this affect the frequency of output voltage ?

• A. Frequency of maximum output voltage is halved.
• B. Frequency of maximum output voltage is doubled.
• C. Frequency of maximum output voltage remains same.
• D. Insufficient data.

Answer 1

The correct option is B Frequency of maximum output voltage is doubled.

In an a.c. generator, emf produced is,

$e=NAB\left(2\pi v\right)sin\left(2\pi v\right)t$

where $N=$ no. of turns

$A=$ cross- sectional area

$B=$ magnetic field.

A frequency of ac, $v=\frac{w}{2\pi }$

where $w=$ is the speed of rotation

From the above, Frequency of maximum output voltage is directly proportional to speed of rotation of coil.

B. Frequency of maximum output voltage is double.