JEE Main · 2019 · 10 Apr 2019 · Shift 1 · Alternating Current

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A transformer consisting of 300 turns in the primary and 150 turns in the secondary gives output power of 2.2 kW. If the current in the secondary coils is 10 A, then the input voltage and current in the primary coil are:

(A)440 V and 5 A✓ Correct
(B)440 and 20 A
(C)220 V and 20 A
(D)220 V and 10 A

Answer: (A)

Solution

The output power and current fix the output voltage:

V_{o} = \frac{P _{o}}{I _{s}} = \frac{2200}{10} = 220

V. For an ideal transformer

\frac{V _{i}}{V _{o}} = \frac{N _{P}}{N _{S}}

, so

V_{i} = 220 \times \frac{300}{150} = 440

V. Power is conserved, so

V_{i} I_{i} = 2200

gives

I_{i} = \frac{2200}{440} = 5

A. The primary runs at

440

V and

5

JEE Main · 2019 · 10 Apr 2019 · Shift 1 · Single correct option

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