Part A

Transformers deal with electrical energy only. In an ideal transformer, the power in the primary coil is equal to the power in the secondary coil. For a step-up transformer, the number of turns in the secondary coil is greater than the number of turns in the primary coil. Transformers work with AC voltages and currents only.

Part A

Which of the following statements are true regarding transformers?

Check all that apply.

a) In a transformer, if the primary coil contains more loops than the secondary coil, then it is a step-up transformer.

b) A transformer converts mechanical energy into electrical energy.

c) A transformer is used to increase or decrease a direct current voltage.

d) A transformer is used to increase or decrease an alternating current voltage.

e) In a transformer, if the secondary coil contains more loops than the primary coil, then it is a step-up transformer.

f) In a transformer, the power input is less than the power output.

Part B

A resistor, an inductor, and a switch are all connected in series to an ideal battery of constant terminal voltage. Suppose at first the switch is open, and then, at some initial time *t* = 0, it is closed. Which of the following statements are true?

Check all that apply.

a) At the instant the switch is closed, the current reaches its steady-state value.

b) The steady-state value of the current depends on the inductance of the inductor.

c) At the instant the switch is closed, the current begins to increase at a rate that depends upon the value of the inductance of the inductor.

d)The steady-state value of the current depends on the resistance of the resistor.

Part C

A resistor, an inductor, and a switch are all connected in series to an ideal battery of constant terminal voltage. What does the time constant for the circuit represent?

a) The time constant represents the time required for the current to reach 25% of the maximum current.

b) The time constant represents the time required for the current to reach 75% of the maximum current.

c) The time constant represents the time required for the current to reach 37% of the maximum current.

d) The time constant represents the time required for the current to reach 63% of the maximum current.

e) The time constant represents the time required for the current to reach 50% of the maximum current.

f) The time constant represents the time required for the current to reach 99% of the maximum current.

Part D

An inductor is connected in series to a fully charged capacitor. Which of the following statements are true?

Check all that apply.

a) The stored electric field energy can be less than the stored magnetic field energy.

b) As the capacitor is discharging, the current is increasing.

c) The stored electric field energy can be equal to the stored magnetic field energy.

d) As the capacitor is charging, the current is increasing.

e) The stored electric field energy can be greater than the stored magnetic field energy.

Frequently Asked Questions

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