Question

The maximum current in a 26 μF capacitor connected to an ac generator with a frequency of 140 Hz is 0.15 A .

Part A

What is the maximum voltage of the generator?

Express your answer using two significant figures.

Vmax =

6.6

V ----> correct answer

Part B

What is the voltage across the capacitor when the current in the circuit is 0.10 A and increasing?

Express your answer using two significant figures.

V = ??? V

I've tried 7.4 but its wrong

Part C

What is the voltage across the capacitor when the current in the circuit is 0.10 A and decreasing?

Express your answer using two significant figures.

V = ???? V

Answer 1

a)

$\omega$ = 2 X 3.14 X 140

$\omega$ = 879.2 rad/sec

X_C = 1 / C $\omega$

X_C = 1 / 26 X 10^-6 X 879.2

= 43.74 ohm

I_max = 0.15 A

Vmax = I_max X X_C

Vmax = 0.15 X 43.74 = 6.56 V

Vmax = 6.6 volts ( rounded off value )

b )

I = I_max cos ( $\omega$ t + $\pi$ /2 )

I = 0.15 X sin $\omega$ t

given current 0.1 A

0.1 = 0.15 sin $\theta$

$\theta$ = 41.81^o or 138.19^o

V = 6.56 X cos41.81

V = 4.88 volts

c )

V = 6.63 X cos138.19

V = - 4.88 volts