A step up transformer is used on 120 V line to provide a P.D. of 2400 V. If the number of turns in primary is 75, then the number of turns in the secondary shall be

 1500 

Here E_P = 120 V, E_S = 24000 V, n_p = 75 and n_s = ?

$\frac{E_s}{E_p} = \frac{n_s}{n_p}$

$\Rightarrow n_s = \frac{E_s}{E_p}\times n_p = \frac{2400}{120} \times 75 = 1500$