A 4.0 ??F and a 1.0 ??F capacitor are connected in parallel and both are charged

Question

A 4.0 ??F and a 1.0 ??F capacitor are connected in parallel and both are charged with a 12. volt battery. They are disconnected from the battery and reconnected positive side of the 1st to negative side of 2nd, and neg. side of 1st to pos. side of 2nd. (a) How much was each charged when connected to the battery? (b) After reconnecting, how much charge is stored? (c) What potential exists across the final parallel combination? 5. The electric potential at the origin of an xy-coordinate system is 40 V. A -8.0-??C charge is brought from x = +?? to that point. What is the electric potential energy of this charge at the origin?

Explanation / Answer

q= V*C

a) 4uF was charged to 12* 4 = 48 uC

1 uF was charged to 12*1 =12 uC

b) When the are re connected the potential either side connected has to be same and the charge on two cpnnected plates must be conserved.

now each connected plate has a total harge of (48-12 )uC= 36 uC

let charge on 4uF be quC charge on 1 uF will be 36-q.

Since potential will be same we have

q/4 = 36-q/1

so q= 28.8

so charge on 4uF =28.8 uC

charge on 1 uF = 7.2 uF

c) potential across final combination = 28.8/4 = 7.2 volts

d) electric potential at a point is defined as the work done to bring a unit positive charge from infinity to that point.

so to bring a -8uC charge potential will be 40 * -8*10^-6= 3.2*10^-4 V

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---