Question

A common transistor radio set requires 12V (D.C.) for its operation. The D.C. source is constructed by using a transformer and a rectifier circuit, which are operated at 220 V (A.C.) on standard domestic A.C. supply. The number of turns of secondary coil are 24, then the number of turns of primary are ______

Answer 1

The correct answer is 440

\({N_p\over N_s}={V_p\over V_s}\) 

\({N_p\over24}={220\over12}\) 

\(N_p={200×24\over12}\) 

\(N_p=440\)