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A transformer is rated 240v. If the primary coil is 4000 turns and the secondary ...

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.
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  • A 200
  • B 100
  • C 250
  • D 150
Correct Answer: Option A
Explanation:
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

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