The primary coil of a transformer has N turns and is connected to a 120 V a.c. power line. If the secondary coils has 1 000 turns and a terminal voltage of 1 200 volts, what is the value of N?
A
120
B
100
C
1 000
D
1 200
Verified Correct Answer: B.
Physical Principles & Numerical Solution
For the transformer, V ∝ ∩
=> V s ∝ ∩s; Vp ∝ ∩p
=> \(\frac{V_p}{V_s} = \frac{∩_p}{∩_s}\), therefore \(\frac{120}{1200} = \frac{∩_p}{1000}\)
therefore ∩\(_p \times 1200 = 120\times 1000\)
∩\(_p = 120\times\frac{1000}{1200}\) = 100
Source: Myschool Past Questions Archive (Record #9097)