In this example we will use the concept of capacitive reactance to determine the

Question

In this example we will use the concept of capacitive reactance to determine the current and voltages in a circuit consisting of a series combination of a capacitor and resistor. A 300 resistor is connected in series with a 5.0 F capacitor, as shown in (Figure 1) . The voltage across the resistor is vR=(1.20V)cos(2500rad/s)t. (a) Derive an expression for the circuit current. (b) Determine the capacitive reactance of the capacitor. (c) Derive an expression for the voltage vC across the capacitor.

A 265 resistor is connected in series with a 4.60 F capacitor. The voltage across the resistor is vR=(1.20V)cos(2500rad/s)t.Determine the capacitive reactance of the capacitor.

Express your answer in ohms to two significant figures.

Explanation / Answer

(A) I = vR /R

I = (4 mA) cos(2500 t)

(b) Xc = 1/wC = 1/(2500 x 5 x 10^-6)

Xc = 80 ohm

(C) Vc = I Xc

Vc = 0.320 Volt cos(2500t + pi/2 )

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Xc = 1/(2500 x 4.60 x 10^-6)

Xc = 87 ohm ......Ans

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