# Physics Class 12 NCERT Solutions: Chapter 2 Electrostatic Potential and Capacitance Part 11

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Q: 24. What is the area of the plates of a parallel plate capacitor, given that the separation between the plates is? [You will realize from your answer why ordinary capacitors are in the range of or less. However, electrolytic capacitors do have a much larger capacitance because of very minute separation between the conductors.]

Answer:

Capacitance of a parallel capacitor,

Distance between the two plates,

Capacitance of a parallel plate capacitor is given by the relation,

Where,

Permittivity of free space

Hence, the area of the plates is too large. To avoid this situation, the capacitance is taken in the range of .

Q: 25. Obtain the equivalent capacitance of the network in Figure. For a supply, determine the charge and voltage across each capacitor.

Answer:

Capacitance of capacitor is .

Capacitance of capacitor is .

Capacitance of capacitor is .

Capacitance of capacitor is .

Supply potential,

Capacitors and are connected in series. Let their equivalent capacitance be .

Capacitors are in parallel. Let their equivalent capacitance be

are connected in series. Let their equivalent capacitance be C.

Hence, the equivalent capacitance of the circuit is

Potential difference across

Potential difference across

Charge on is given by,

Voltage across is given by,

Hence, potential difference, across is .

Charge on is given by,

And having same capacitances have a potential difference of together. Since and are in series, the potential difference across and is given by,

Therefore, charge on is given by,

And charge on is given by,

Hence, the equivalent capacitance of the given circuit is with,