# physics

posted by .

A 20.0 \mu F capacitor initially charged to 20.0 \mu C is discharged through a 1.90 k\Omega resistor. How long does it take to reduce the capacitor's charge to 5.00 \mu C?

• physics -

The charge of the discharging capacitor, as a function of t, is:

Q(t) = Qo* e^(-t/RC)

Qo is the initial charge, RC is the time constant, which in this case is 1900*20*10^-6 = 0.038 seconds

So, solve

5*10^-6 = 20*10^-6*e^(-t/0.038)

ln(1/4) = -t/0.038

t = ?

## Similar Questions

1. ### Physics

A capacitor of capacitance C= 10mF, is charged using a battery of potential V, through a resistor of resistance R = 250 ohms. the charge of the capacitor is given by Q(t)=CV[1− e ^ (−t/RC)] Find an expression for the current …
2. ### physics

A fully charged 98 uF capacitor is discharged through a 125 ohms resistor. How long will it take for the capacitor to lose 75% of its initial energy
3. ### physics

A 9 V battery is connected in series with a 100 Ω resistor and 12µF capacitor. The capacitor is initially uncharged. What is the capacitive time constant of the circuit?
4. ### Physics

A fully charged 90-µF capacitor is discharged through a 60-Ω resistor. How long will it take for the capacitor to lose 80% of its initial energy?
5. ### Physics

A 6 uF capacitor is initially charged to 100V and then connected across a 600 ohm resistor. a) what is the initial charge on the capacitor?
6. ### physics

A resistor with 780 is connected to the plates of a charged capacitor with capacitance 4.32 . Just before the connection is made, the charge on the capacitor is 7.80 1)What is the energy initially stored in the capacitor?
7. ### Physic II

Suppose a capacitor having a capacitance of C fully charged to a voltage V and then discharged through a resistor R. Derive the equation (in terms of C,V,and R) that shows how long a time the capacitor will take to lose 45 % of its …
8. ### Physics

A 600W flashlamp fitted to a camera is operated by discharging a 10 000 uF capacitor through the lamp. The capacitor is charged initially from a 6V battery. Calculate A) the energy stores in the capacitor when fully charged B) the …
9. ### physics

determine the a)charge on the capacitor b)voltage across the capacitor c)current through the resistor after t=rc when a capacitor is getting charged interms of their peak values
10. ### Physics

A 14.1 μF capacitor is charged to a potential of 45.0 V and then discharged through an 80.0 Ω resistor. (a) How long after discharge begins does it take for the capacitor to lose 90.0% of the following?

More Similar Questions