Experiment 5: Resonance in an LRC Circuit

When a series LRC circuit is driven at its resonance frequency, the phase difference between the drive voltage and the voltage across the resistor will be (a) 180 out of phase (b) 90 out of phase (c) 0 or in-phase.

0 degrees out of phase

Find the resonance frequency fo of an LRC circuit with L = 0.03 H, C = nF and R = 1 kΩ.

29000

Find the quality factor Q of a series LRC circuit with L = 0.03 H, C = 1 nF and R = 1 kΩ.

5.5

In Part C of this experiment, an aluminum rod is placed in the core of the inductor. Should the resonance frequency of the LRC circuit (a) increase (b) decrease

A, increase

When the LRC circuit in this experiment is driven at its resonance frequency, the voltage across the resistor will be: (a) at zero voltage (b) at a minimum and equal to the driving voltage (c) at a maximum and equal to the driving voltage (d) at a maximum and Q times the driving voltage.

B, At a maximum and equal to the driving voltage

In Part C of this experiment, an iron rod is placed in the core of the inductor. Should the resonance frequency of the LRC circuit (a) increase (b) decrease (c) not change (d) there is no way to determine the answer from the information given.

B, decrease

How can we increase the resonant frequency of an LRC circuit?

Decrease inductance(L) or capacitance(C)

How can we make the Q of an LRC circuit larger?

Increase resonant frequency, increase inductance, or decrease resistance R Q=(w0*L)/R

Experiment 5 Purpose

Observe the behavior of an electrical resonator formed by connecting an inductor L in series with a capacitor C and a resistor R.

Explain the difference between impedance and resistance

Resistance is the opposition of current flow in DC or AC circuits caused by resistors, impedance is the opposition of current flow in AC circuits caused by resistors, capacitors, and inductors (impedance is in AC current)

A series LRC circuit is driven on resonance with a driving voltage amplitude of Vo = 1 V. If the quality factor Q = 20, what is the amplitude VR of the voltage across the resistor?

V=1

A series LRC circuit is driven at a frequency which is much less than the resonant frequency with a sine wave voltage source V0sin(ωt). What is the approximate voltage across the capacitor? Briefly explain.

Vc=emf; at low frequencies almost all the "drive voltage" is across the capacitor (where it has the largest impedance), at high frequencies almost all the drive voltage is across the inductor (where it has the largest impedance)

A series LRC circuit is driven at resonance with a sine wave voltage source. What is the sum of the voltages across the inductor and the capacitor in an ideal circuit? Briefly explain.

Vtotal=0; Vl=Vc at resonance

Can the voltage across the capacitor in a series LRC circuit be larger than the voltage across the voltage source? Briefly explain

Yes, when the charge in the capacitor is at its max

Can the voltage across the inductor in a series LRC circuit be larger than the voltage across the voltage source? Briefly explain.

Yes, when the current through the inductor is at its max