Complete Electronics Self-Teaching Guide with Projects

Capacitors in AC Circuits

12 A capacitor opposes the flow of an AC current.

Questions

A. What is this opposition to the current flow called? _____

B. What is this similar to in DC circuits? _____

Answers

A. Reactance

B. Resistance

13 Just as with resistance, you determine reactance by using an equation.

Questions

A. What is the equation for reactance? _____

B. What does each symbol in the equation stand for? _____

C. How does the reactance of a capacitor change as the frequency of a signal increases? _____

Answers

A.

B. X_C = the reactance of the capacitor in ohms.

f = the frequency of the signal in hertz.

C = the value of the capacitor in farads.

C. The reactance of a capacitor decreases as the frequency of the signal increases.

14 Assume the capacitance is 1 μF and the frequency is 1 kHz.

Question

Find the capacitor's reactance. (Note: 1/(2π) = 0.159, approximately.) _____

Answers

f = 1 kHz = 10³ Hz

C = 1 μF = 10⁻⁶ F

Thus,

15 Now, perform these simple calculations. In each case, find X_C1 (the capacitor's reactance at 1 kHz) and X_C2 (the capacitor's reactance at the frequency specified in the question).

Questions

Find X_C1 and X_C2: ...