JAMB - Physics (2001 - No. 29)
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?
120
100
1 000
1 200
Explanation
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
=> 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
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