ISCET AC Circuits and Analysis 5

Question 1

In a series RLC circuit, if XL > XC, the circuit is said to be:

Accepted Answer

Inductive and current lags voltage

Answer

When XL > XC, the net reactance is inductive, so the circuit behaves inductively and current lags behind voltage.

Question 2

The average (DC equivalent) value of a full-wave rectified sine wave with peak value Vpeak is:

Accepted Answer

0.636 × Vpeak

Answer

The average value of a full-wave rectified sine is Vavg = (2/π) × Vpeak ≈ 0.636 × Vpeak.

Question 3

Impedance matching between a source and load in an AC system is important primarily to:

Accepted Answer

Maximize power transfer from source to load

Answer

Maximum power is transferred when the load impedance equals the complex conjugate of the source impedance.

Question 4

An oscilloscope shows a sine wave with a period of 4 ms. What is its frequency?

Accepted Answer

250 Hz

Answer

Frequency f = 1/T = 1/0.004 s = 250 Hz.

Question 5

In a 60 Hz AC power system, an inductor of 100 mH has an inductive reactance of approximately:

Accepted Answer

37.7 Ω

Answer

XL = 2πfL = 2π × 60 × 0.1 ≈ 37.7 Ω.

(ISCET) International Society of Certified Electronics Technicians Practice Test