AC Circuit(2)

Multiple Choice

An AC source drives an RLC circuit with a fixed voltage amplitude. If the driving frequency is ω_1, the circuit is more capacitive than inductive and the phase angle is -10°. If the driving frequency is ω_2, the circuit is more inductive than capacitive and the phase angle is +10°.  At what frequency is the largest amount of power delivered to the circuit?

• It is largest at ω1

• It is largest at ω2

• The same amount of power is delivered at both frequencies.

Fill in the Blank

The resistance in a series RCL circuit is doubled.

(a) Does the resonant frequency increase, decrease, or remain the same?

(b) Does the maximum current in the circuit increase, decrease, or remain the same?

(a)____(i/d/s)

(b)____(i/d/s)

Multiple Choice

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

• The current leads the voltage.

• The current lags behind the voltage.

• The current is in phase with the current.

Open Ended

Is it possible for two series RCL circuits to have the same resonant frequencies and yet have

(a) different R values

(b) different C and L values?

Multiple Choice

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 (a) in series or (b) in parallel with the one already present?

• in series

• in parrallel

Multiple Choice

A transformer changes the 120-V voltage at a wall socket to 12 000 V. The current delivered by the wall socket is

• increased by a factor of 100

• decreased by a factor of 100

• neither increase nor decrease

Multiple Select

A transformer that stepped up the voltage and the current simultaneously would

• produce less power at the secondary coil than was supplied at the primary coil

• produce more power at the secondary coil than was supplied at the primary coil

• produce the same amount of power at the secondary coil that was supplied at the primary coil

• violate the law of conservation of energy.