JEE Main · 2013 · 07 Apr 2013 · Offline · Capacitance

Two capacitors

C_{1}

and

C_{2}

are charged to 120 V and 200 V respectively. It is found that by connecting them together the potential on each one can be made zero. Then :

(A) $3 C_{1} = 5 C_{2}$ ✓ Correct
(B) $3 C_{1} + 5 C_{2} = 0$
(C) $9 C_{1} = 4 C_{2}$
(D) $5 C_{1} = 3 C_{2}$

Answer: (A)

Solution

If joining the two charged capacitors can bring the potential on each to zero, their charges must be equal in size and opposite in sign so they cancel when the plates are connected. Equal charge magnitudes means

C_{1} (120) = C_{2} (200)

, which tidies to

3 C_{1} = 5 C_{2}

JEE Main · 2013 · 07 Apr 2013 · Offline · Single correct option

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