Which of the following are true? (Select all that apply.) (a) A transformer is u

Question

Which of the following are true? (Select all that apply.)

(a) A transformer is used to change frequency. (b) A transformer is used to change voltage. (c) If a transformer steps up the current, it must step down the voltage. (d) A step-up transformer steps down the current. (e) The standard household wall-outlet voltage in Europe is 220 V, about twice that used in the United States. If a European traveler wants her hair dryer to work properly in the United States, she should use a transformer that has more windings in its secondary coil than in its primary coil. (f) The standard household wall-outlet voltage in Europe is 220 V, about twice that used in the United States. If an American traveler wants his electric razor to work properly in Europe, he should use transformer that steps up the current.

Explanation / Answer

The true ones are:

(b) A transformer is used to change voltage. (either to increase (step-up) or to decrease (step-down)).

(step-up transformer steps-up the voltage and hence steps-down the current).

(f) The standard household wall-outlet voltage in Europe is 220 V, about twice that used in the United States. If an American traveler wants his electric razor to work properly in Europe, he should use transformer that steps up the current. (obviously since the coltage needs to be increased, step up transformer has to be used)

False ones:

(a) A transformer is used to change frequency. (under any circumstance, frequency is not changed. It is always constant).

(e) The standard household wall-outlet voltage in Europe is 220 V, about twice that used in the United States. If a European traveler wants her hair dryer to work properly in the United States, she should use a transformer that has more windings in its secondary coil than in its primary coil.

(He has to step-down the voltage, so he will need lesser number of windings in the secondary)

(c) If a transformer steps up the current, it must step down the voltage.

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