In a television set the power needed to operate the picture tube comes from the secondary of a transformer. the primary of the transformer is connected to a 120-v receptacle on a wall. the picture tube of the television set uses 91 w, and there is 5.5 ma of current in the secondary coil of the transformer to which the tube is connected. find the turns ratio ns/np of the transformer.

  138 for the ratio Ns/Np

Explanation: In order to explain this question we have to take into account the relationship for transformer wichi os given by ;

Vs=Vp Ns/Np where Vs and Vp are the voltage corresponding to the secondary and primary coil of the transformer, respectively. Ns and Np are the turns for the secondary and primery coil , respectively.

Firsly  we have to calculate Vs which is given by power (91W) and current (5.5 mA) used. Then

Ps=Is*Vs=

Vs=91W/5.5 mA=16.54 *10^3 V so

Vs/Vp=Ns/Np

Ns/Np=16.54*10^3/120=138