The primary coil of a transformer has N turns and is connected to a 120 V a.c. power line. If the secondary coils have 1000 turns and a terminal voltage of 1200 volts, what is the value of N?

A. 120
B. 100
C. 1000
D. 1200

Correct Answer:

Option B = 100

Explanation

For the transformer, V ∝ ∩
=> V s ∝ ∩s; Vp ∝ ∩p
=> Vp/Vs = ∩p/∩s, therefore 120/1200 = ∩p/1000
therefore ∩p * 1200 = 120 * 1000
∩p = 120*1000/1200 = 100