Worksheet 15-Capacitive Reactance

Question 1

Referring to the graph, what is implied about the circuit when the plotted arrow is pointing down?

Answer 1

When the arrow on the plot is less than 0 (X_C<0), it means that the circuit has net capacitive reactance.

Question 2

Write out the mathematical formula for X_C.

Answer 2

X_C = 1 / 2 ∏ f C

Question 3

What is the mathematical relationship between frequency and capacitance to capacitive reactance?

Answer 3

X_C is inversely proportional to both frequency and capacitance.

Question 4

Determine the X_C when: 2μF capacitor and 50Hz input.

Answer 4

X_C = 1 / 2 ∏ f C

X_C = 1 / 6.28 x 50Hz x 0.000002H

X_C = 1 / 0.000628319

X_C = 1,591.58Ω

Question 5

Determine the X_C when: 5μF capacitor and 120Hz input.

Answer 5

X_C = 1 / 2 ∏ f C

X_C = 1 / 6.28 x 120Hz x 0.000005H

X_C = 1 / 0.003769911

X_C = 265.25Ω

Question 6

What is the formula for X_CT for capacitors in series?

Answer 6

X_CT = X_C1 + X_C2 + X_C3 +…… X_CN

Question 7

Determine the X_CT for this circuit.

Answer 7

1/X_CT = 1/X_C1 + 1/X_C2 + 1/X_C3

1/X_CT = 1/21 + 1/42 + 1/42

X_CT = 1 / 0.047619048+0.023909624+0.023809524

1/X_CT = 10.5Ω