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The primary of a transformer when connected to a dc battery of 10 volt draws a current of 1 mA. The number of turns of the primary and secondary windings are 50 and 100 respectively. The voltage in the secondary and the current drawn by the circuit in the secondary are respectively

1. 20 V and 0.5 mA
2. 20 V and 2.0 mA
3. 10 V and 0.5 mA
4. Zero and therefore no current

Correct answer: Zero and therefore no current

Solution

A transformer does not work with DC voltage because it relies on a changing magnetic flux to induce voltage in the secondary coil. With a DC source, there is no change in flux, so the secondary voltage and current are both zero.

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