Multiple Choice
The peak current to and from an inductor is i when the emf source has a peak voltage V and frequency f. What is the peak current to and from the inductor if the frequency and peak voltage are doubled to 2f and 2V, respectively?
31. Alternating Current
Inductors in AC Circuits
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A certain laptop charger says that the provided to the laptop is 12 V. You know this charger is plugged into an outlet for which is 120 V, such that there must be a transformer inside the laptop charger. If the number of windings of wire on the laptop side of the transformer is 60, how many windings of wire must be on the outlet side of the transformer?
A
2
B
6
C
10
D
120
E
240
F
600
Verified step by step guidance1
Understand that a transformer is a device that transfers electrical energy between two or more circuits through electromagnetic induction. It consists of two windings: the primary winding (connected to the input voltage) and the secondary winding (connected to the output voltage).
Recall the transformer equation, which relates the voltages and the number of turns in the windings: \( \frac{V_{\text{primary}}}{V_{\text{secondary}}} = \frac{N_{\text{primary}}}{N_{\text{secondary}}} \), where \( V \) represents voltage and \( N \) represents the number of turns.
Identify the given values: \( V_{\text{primary}} = 120 \text{ V} \), \( V_{\text{secondary}} = 12 \text{ V} \), and \( N_{\text{secondary}} = 60 \). We need to find \( N_{\text{primary}} \).
Rearrange the transformer equation to solve for \( N_{\text{primary}} \): \( N_{\text{primary}} = N_{\text{secondary}} \times \frac{V_{\text{primary}}}{V_{\text{secondary}}} \).
Substitute the known values into the equation: \( N_{\text{primary}} = 60 \times \frac{120}{12} \). Calculate this expression to find the number of windings on the outlet side of the transformer.
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