University Physics Volume 2

# Conceptual Questions

University Physics Volume 2Conceptual Questions

### 15.1AC Sources

1.

What is the relationship between frequency and angular frequency?

### 15.2Simple AC Circuits

2.

Explain why at high frequencies a capacitor acts as an ac short, whereas an inductor acts as an open circuit.

### 15.3RLC Series Circuits with AC

3.

In an RLC series circuit, can the voltage measured across the capacitor be greater than the voltage of the source? Answer the same question for the voltage across the inductor.

### 15.4Power in an AC Circuit

4.

For what value of the phase angle $ϕϕ$ between the voltage output of an ac source and the current is the average power output of the source a maximum?

5.

Discuss the differences between average power and instantaneous power.

6.

The average ac current delivered to a circuit is zero. Despite this, power is dissipated in the circuit. Explain.

7.

Can the instantaneous power output of an ac source ever be negative? Can the average power output be negative?

8.

The power rating of a resistor used in ac circuits refers to the maximum average power dissipated in the resistor. How does this compare with the maximum instantaneous power dissipated in the resistor?

### 15.6Transformers

9.

Why do transmission lines operate at very high voltages while household circuits operate at fairly small voltages?

10.

How can you distinguish the primary winding from the secondary winding in a step-up transformer?

11.

Battery packs in some electronic devices are charged using an adapter connected to a wall socket. Speculate as to the purpose of the adapter.

12.

Will a transformer work if the input is a dc voltage?

13.

Why are the primary and secondary coils of a transformer wrapped around the same closed loop of iron?