A `100 mu F` capacitor is charged to a potential difference of `24 V`. It is connected to an uncharged capacitor of capacitance `20 mu F` What will be the new potential difference across the `100 mu F` capacitor?

Explanation

`C_1 = 100 pF , V = 25 V `
Uncharged capacitor of capacitance
`C2 = 20 pF `
Total charge `q = C_1 V = 24 xx 100 pF`
When the charge capacitor is connected with the uncharged capacitor
` q_1 + q_2 = 24 xx 100 qF and `q_1 / C_1 = q_1 / C_1`
q_1 / 100 = q_1 / 20 `
or q_1 = 5 q_2`
From equation (i) and (ii) , we have
` q_1 = 20 xx 100pF`
`v_1 = q_1 / C_1 `
`= 20 xx 100 pF / 20 pF = 20 V`