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# True and False Questions about Transformers

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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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https://brainmass.com/physics/power/true-false-questions-transformers-313096

## SOLUTION This solution is FREE courtesy of BrainMass!

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 varying current.

2. False. In an ideal transformer (which has no losses), the input power = output power. As power = voltage x current, lower voltage on the secondary side must result in higher secondary current so that power is constant.

3. False. Voltage on either side is given by : emf induced per turn x number of turns. Hence, for higher voltage on secondary side, number of secondary turns must be greater than number of primary turns.

4. False. Power is generally transported at high voltage from the power plant to the areas of utilization where the voltage is stepped down to the required lower value (say 220 V, 110 V etc for house holds).

5. False. As mentioned above, in an ideal transformer, average power input = average power output. In a practical transformer, on account of losses, power output < power input.

This content was COPIED from BrainMass.com - View the original, and get the already-completed solution here!

© BrainMass Inc. brainmass.com September 28, 2022, 9:21 pm ad1c9bdddf>
https://brainmass.com/physics/power/true-false-questions-transformers-313096