A transformer is rated 240v. If the primary coil is 4000 turns and the secondary voltage 12v, determine the number of turns in the secondary coil.
A
200
B
100
C
250
D
150
Verified Correct Answer: A.
Physical Principles & Numerical Solution
in a transformer, E S/E P = N s/N p
where E s=e.m.f(voltage)of the secondary
E p=e.m.f(voltage)of the primary
N s=no.of turns in the secondary
N p= no. of turns in the primary.
since E s= V s; and E p= V p.
V s/ V p= N s/N p
∴12/240= Ns/4000
Ns =(12x4000)/240
=200
Source: Myschool Past Questions Archive (Record #13718)