1. Q31.1
A resistor is connected across an ac source as shown. Which graph correctly shows the instantaneous current through the resistor and the instantaneous voltage vab across the resistor?
(current in purple, voltage in blue) 1. 2. 3.

2. A31.1
A resistor is connected across an ac source as shown. Which graph correctly shows the instantaneous current through the resistor and the instantaneous voltage vab across the resistor?
(current in purple, voltage in blue) 1. 2. 3.

3. Q31.2
An inductor is connected across an ac source as shown. Which graph correctly shows the instantaneous current through the inductor and the instantaneous voltage vab across the inductor?
(current in purple, voltage in blue) 1. 2. 3.

4. A31.2
An inductor is connected across an ac source as shown. Which graph correctly shows the instantaneous current through the inductor and the instantaneous voltage vab across the inductor?
(current in purple, voltage in blue) 1. 2. 3.

5. Q31.3
A capacitor is connected across an ac source as shown. Which graph correctly shows the instantaneous current through the capacitor and the instantaneous voltage vab across the capacitor?
(current in purple, voltage in blue) 1. 2. 3.

6. A31.3
A capacitor is connected across an ac source as shown. Which graph correctly shows the instantaneous current through the capacitor and the instantaneous voltage vab across the capacitor?
(current in purple, voltage in blue) 1. 2. 3.

7. Q31.4
An L-R-C series circuit as shown is operating at its resonant frequency. At this frequency, how are the values of the capacitive reactance XC, the inductive reactance XL, and the resistance R related to each other?
1. XL = R; XC can have any value
2. XC = R; XL can have any value
3. XC = XL; R can have any value
4. XC = XL = R
5. none of the above

8. A31.4
An L-R-C series circuit as shown is operating at its resonant frequency. At this frequency, how are the values of the capacitive reactance XC, the inductive reactance XL, and the resistance R related to each other?
1. XL = R; XC can have any value
2. XC = R; XL can have any value
3. XC = XL; R can have any value
4. XC = XL = R
5. none of the above

9. Q31.5
In an L-R-C series circuit as shown, the current has a very small amplitude if the emf oscillates at a very high frequency. Which circuit element causes this behavior?
1. the resistor R
2. the inductor L
3. the capacitor C
4. misleading question — the current actually has a very large amplitude if the frequency is very high

10. A31.5
In an L-R-C series circuit as shown, the current has a very small amplitude if the emf oscillates at a very high frequency. Which circuit element causes this behavior?
1. the resistor R
2. the inductor L
3. the capacitor C
4. misleading question — the current actually has a very large amplitude if the frequency is very high

11. Q31.6
In an L-R-C series circuit as shown, there is a phase angle between the instantaneous current through the circuit and the instantaneous voltage vad across the entire circuit. For what value of the phase angle is the greatest power delivered to the resistor?
1. zero
2. 90°
3. 180°
4. 270°
5. none of the above

12. A31.6
In an L-R-C series circuit as shown, there is a phase angle between the instantaneous current through the circuit and the instantaneous voltage vad across the entire circuit. For what value of the phase angle is the greatest power delivered to the resistor?
1. zero
2. 90°
3. 180°
4. 270°
5. none of the above

13. Q31.7
In the transformer shown in the drawing, there are more turns in the secondary than in the primary. In this situation,
1. the current amplitude is greater in the primary than in the secondary
2. the current amplitude is smaller in the primary than in the secondary
3. the current amplitude is the same in the primary and in the secondary
4. not enough information given to decide

14. A31.7
In the transformer shown in the drawing, there are more turns in the secondary than in the primary. In this situation,
1. the current amplitude is greater in the primary than in the secondary
2. the current amplitude is smaller in the primary than in the secondary
3. the current amplitude is the same in the primary and in the secondary
4. not enough information given to decide