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True and False Questions about Transformers

A transformer is an electrical device that can change the voltage from one value to another, based on the principle of Faraday's Law of Induction. Consider a transformer with Np turns of wire in the primary (input) circuit and Ns turns in the secondary (output). Which of the following statements are true? Briefly justify your answers.

1. Transformers can only work with DC voltages (not AC).

2. If the secondary voltage is lower than the primary voltage, then the secondary current is also lower than the primary current.

3. To have a higher voltage on the secondary, Ns < Np.

4. Transformers in your neighborhood step up the voltage from power plants so that there is plenty of electricity to run your many home appliances.

5. If Ns > Np, the average power in the secondary is greater than the average power in the primary.

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Solution Preview

1. False. Transformer works on the principle of induced emf in a coil placed in a varying magnetic field. In case of DC, the current does not vary, hence there is no varying magnetic field, hence no induced emf. In case of AC there is a varying magnetic field on account of ...

Solution Summary

This solution provides answers to the true and false questions about transformers with an explanation for each.