Conceptual Questions

ssm Solution is in the Student Solutions Manual.

| 1 | A light bulb and a parallel plate capacitor (containing a dielectric material between the plates) are connected in series to the 60-Hz ac voltage present at a wall outlet. Describe what happens to the brightness of the bulb when the dielectric material is removed from the space between the plates. Explain.

| 2 | ssm The ends of a long, straight wire are connected to the terminals of an ac generator, and the current is measured. The wire is then disconnected, wound into the shape of a multiple-turn coil, and reconnected to the generator. In which case, if either, does the generator deliver a larger current? Account for your answer.

| 3 | An air-core inductor is connected in series with a light bulb, and this circuit is plugged into an electrical outlet. What happens to the brightness of the bulb when a piece of iron is inserted inside the inductor? Give a reason for your answer.

| 4 | Consider the circuit in Figure 23-9. With the capacitor and the inductor present, a certain amount of current is in the circuit. Then the capacitor and the inductor are removed, so that only the resistor remains connected to the generator. Is it possible that the current in the simplified circuit has the same rms value as that in the original circuit? Give your reasoning.

| 5 | Can an ac circuit, such as the one in Figure 23-9, have the same impedance at two different generator frequencies? Justify your answer.

| 6 | Review Conceptual Example 5 as an aid in understanding this question. An inductor and a capacitor are connected in parallel across the terminals of a generator. What happens to the current from the generator as the frequency becomes (a) very large and (b) very small? Give your reasoning.

| 7 | ssm Review Conceptual Example 5. For which of the two circuits discussed there does the generator deliver more current when the frequency is very large? Account for your answer.

| 8 | In a series RCL circuit at resonance, does the current lead or lag behind the voltage across the generator or is it in phase with the voltage? Explain.

| 9 | Is it possible for two series RCL circuits to have the same resonant frequencies and yet have (a) different R values and (b) different C and L values? Justify your answers.

| 10 | Suppose the generator connected to a series RCL circuit has a frequency that is greater than the resonant frequency of the circuit. Suppose, in addition, that it is necessary to match the resonant frequency of the circuit to the frequency of the generator. To accomplish this, should you add a second capacitor in series or in parallel with the one already present? Explain your choice.

| 11 | ssm The drawing shows a full-wave rectifier circuit, in which the direction of the current through the load resistor R is the same for both positive and negative halves of the generator’s voltage cycle. Draw the current through the circuit when (a) the top of the generator is positive and the bottom is negative and (b) the top of the generator is negative and the bottom is positive.

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