The circuit below was at position a for a long time. It is suddenly switched to

Question

The circuit below was at position a for a long time. It is suddenly switched to position b at time t=0.

1.

(For each statement select T True, F False).

A) In the instant after the switch is thrown, the voltage across the capacitor is zero.
B) In the instant after the switch is thrown the current through the capapacitor is zero.
C) In the instant after the switch is thrown the voltage across the resistor is zero.
D) The current through the resistor equals the current through the capacitor at all times.

2. In the previous problem, if the battery provides a voltage V = 3.75 V, the capacitor has C = 14.0 ?F and the resistor has R = 600.0 ?, what is the capacitor voltage Vc at time t = 0.9 ms?

3.In the previous problem, what is the total energy dissipated in the resistor after time t = 0?

4. For the circuit in the previous problem, consider the case when the switch is in position b for a long time, then switched to position a at time t = 0. What is the capacitor voltage Vc at time t = 1.6 ms?

Explanation / Answer

A)

false.

Since the switch a was closed for a long time , so the capacitor gets fully charged and have Voltage equal to the voltage of battery before the swicth is thrown to b .

just after switch is thrown to b , the Voltage across capacitor is same as the voltage across the battery

B)

True

Since capacitor is fully charged , no current flows

C)

False

Resistance is in parallel with the capacitor , hence it will same voltage as the capacitor

D)

True.

2

T = time constant = RC = 600 x 14 x 10-6 = 0.0084 sec

t = time given = 0.9 x 10-3 sec = 0.0009 sec

Vo = maximum Voltage = 3.75 volts

V = Vo (1 - e^-t/T)

V = 3.75 (1 - e^-(0.0009/0.0084))

V = 0.381 volts

3.

Total energy dissipated = total energy stored by capacitor = (0.5) C Vo2 = (0.5) (14 x 10-6) (3.75)2 = 9.84 x 10-5 J

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.