# Extra Class Exam Question Pool

effective 7/01/2008 thru 6/30/2012

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E5B: Time constants and phase relationships: R/L/C time constants: definition; time constants in RL and RC circuits; phase angle between voltage and current; phase angles of series and parallel circuits

E5B01: What is the term for the time required for the capacitor in an RC circuit to be charged to 63.2% of the supply voltage?

One time constant

An exponential rate of one

One exponential period

A time factor of one

E5B02: What is the term for the time it takes for a charged capacitor in an RC circuit to discharge to 36.8% of its initial value of stored charge?

One time constant

One discharge period

An exponential discharge rate of one

A discharge factor of one

E5B03: The capacitor in an RC circuit is discharged to what percentage of the starting voltage after two time constants?

13.5%

86.5%

63.2%

36.8%

E5B04: What is the time constant of a circuit having two 220-microfarad capacitors and two 1-megohm resistors all in parallel?

220 seconds

55 seconds

110 seconds

440 seconds

E5B05: How long does it take for an initial charge of 20 V DC to decrease to 7.36 V DC in a 0.01-microfarad capacitor when a 2-megohm resistor is connected across it?

0.02 seconds

0.04 seconds

20 seconds

40 seconds

E5B06: How long does it take for an initial charge of 800 V DC to decrease to 294 V DC in a 450-microfarad capacitor when a 1-megohm resistor is connected across it?

450 seconds

4.50 seconds

9 seconds

900 seconds

E5B07: What is the phase angle between the voltage across and the current through a series R-L-C circuit if XC is 500 ohms, R is 1 kilohm, and XL is 250 ohms?

14.0 degrees with the voltage lagging the current

68.2 degrees with the voltage leading the current

14.0 degrees with the voltage leading the current

68.2 degrees with the voltage lagging the current

E5B08: What is the phase angle between the voltage across and the current through a series R-L-C circuit if XC is 100 ohms, R is 100 ohms, and XL is 75 ohms?

14 degrees with the voltage lagging the current

14 degrees with the voltage leading the current

76 degrees with the voltage leading the current

76 degrees with the voltage lagging the current

E5B09: What is the relationship between the current through and the voltage across a capacitor?

Current leads voltage by 90 degrees

Voltage and current are in phase

Voltage and current are 180 degrees out of phase

Voltage leads current by 90 degrees

E5B10: What is the relationship between the current through an inductor and the voltage across an inductor?

Voltage leads current by 90 degrees

Current leads voltage by 90 degrees

Voltage and current are 180 degrees out of phase

Voltage and current are in phase

E5B11: What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 25 ohms, R is 100 ohms, and XL is 50 ohms?

14 degrees with the voltage leading the current

14 degrees with the voltage lagging the current

76 degrees with the voltage lagging the current

76 degrees with the voltage leading the current

E5B12: What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 75 ohms, R is 100 ohms, and XL is 50 ohms?

14 degrees with the voltage lagging the current

76 degrees with the voltage lagging the current

14 degrees with the voltage leading the current

76 degrees with the voltage leading the current

E5B13: What is the phase angle between the voltage across and the current through a series RLC circuit if XC is 250 ohms, R is 1 kilohm, and XL is 500 ohms?

14.04 degrees with the voltage leading the current

81.47 degrees with the voltage lagging the current

81.47 degrees with the voltage leading the current

14.04 degrees with the voltage lagging the current

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