A capacitor \(C_1=6 \mu \mathrm{~F}\), initially charged with a cell of emf 5 V is disconnected and connected to another…
A capacitor \(C_1=6 \mu \mathrm{~F}\), initially charged with a cell of emf 5 V is disconnected and connected to another capacitor \(C_2=12 \mu \mathrm{~F}\) which is initially neutral. The charges on \(C_1\) and \(C_2\) after connection are
(Shift - II Memory Based)
\(10 \mu \mathrm{C}, 20 \mu \mathrm{C}\)
The charge on a capacitor is given by:
\(Q=CV\)
Given:
- \({C}_{1}=6\mu F\)
- \(V=5V\)
\({Q}_{1}=(6\times 1{0}^{−6}F)\times (5V)=30\mu C\)
Since \({C}_{2}\) is initially uncharged, its initial charge is:
\({Q}_{2}=0\mu C\)
Step 2: Charge ConservationWhen the two capacitors are connected, charge redistributes while maintaining charge conservation:
\({Q}_{\text{total}}={Q}_{1}+{Q}_{2}=30\mu C+0=30\mu C\)
Step 3: Common Voltage after ConnectionSince the capacitors are connected in parallel, they share a common voltage \({V}_{f}\):
\({V}_{f}=\frac{{Q}_{\text{total}}}{{C}_{1}+{C}_{2}}\)
\({V}_{f}=\frac{30\mu C}{(6+12)\mu F}\)V
\({V}_{f}=\frac{30}{18}V=\frac{5}{3}V\)
Step 4: Finding Final ChargesUsing \(Q=CV\)
- Final charge on \({C}_{1}\):
\({Q}_{1}^{′}={C}_{1}{V}_{f}=(6\mu F)\times \frac{5}{3}V\)
\({Q}_{1}^{′}=10\mu C\)
- Final charge on \({C}_{2}\):
\({Q}_{2}^{′}={C}_{2}{V}_{f}=(12\mu F)\times \frac{5}{3}V\)
\({Q}_{2}^{′}=20\mu C\)
Step 5: Selecting the Correct OptionThe charges on \({C}_{1}\) and \({C}_{2}\) after connection are:
\(B\ 10\mu C,20\mu C\)
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