When the Turns Ratio of Transformer is 20

Answer: C. 240 V

When the turns ratio of a step-up-transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is 240 V.

Solution

In a step-up transformer primary winding (or the winding for which AC voltage source is connected) voltage will be smaller than secondary winding. For this to be accomplished, the number of turns on secondary winding (N_S) should be greater than primary winding turns (N_P).

Given, 

Turns ratio (or) voltage ratio of transformer a=N_S/N_P=V_S/V_P=20

Primary voltage V_P=12 V

Then, secondary voltage V_S=a×V_P

V_S=20×12 V

V_S=240 V

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