Question

A 10 µF capacitor is fully charged across a 15 V battery. It is then disconnected from the battery and connected to an uncharged capacitor. If the voltage across the capacitor becomes 5 V then the capacitance of the uncharged capacitor will be ____________.

पर्याय

• 5 µF

• 150 µF

• 20 µF

• 60 µF

Answer 1

A 10 µF capacitor is fully charged across a 15 V battery. It is then disconnected from the battery and connected to an uncharged capacitor. If the voltage across the capacitor becomes 5 V then the capacitance of the uncharged capacitor will be 20 µF.

Explanation:

`"Charge on capacitor" = "Q" = "CV"`

`= 10 xx 10^-6 xx 15`

`= 150  mu"C"`

`"Total capacity" = "C" = "C"_1 + "C"_2`

`therefore  "P.D, V" = "Q"/"C" = 150/("C"_1 + "C"_2) = 5 "V"`

`"C"_1 + "C"_2 = 150/5 = 30mu "F"`

`therefore "C"_2 = 30 - "C"_1 = 30 - 10 = 20 mu"F"`