Physics · Electrostatic Potential And Capacitance · NEET
No. This is the most common confusion. Although the formula is C = Q/V, capacitance is a fixed property of the capacitor's shape and size (plate area, gap, and the insulator). When you push in more charge Q, the voltage V rises by the same factor, so the ratio Q/V stays constant. C tells you the ratio, it does not depend on how much charge you actually put in.
A capacitor is the physical object: two conductors with an insulator between them (like two metal plates). Capacitance is a number that describes that object, telling you how good it is at storing charge per volt. So the capacitor is the 'thing' and capacitance is its 'rating'. NEET often mixes these words in questions, so read carefully.
1 farad means the capacitor stores 1 coulomb of charge when 1 volt is applied across it (1 F = 1 C/V). 1 farad is very large, so real capacitors are usually in microfarad (1 uF = 10^-6 F) or picofarad (1 pF = 10^-12 F). Most NEET numerical values are in uF or pF.
Capacitance depends only on the geometry (plate area A, separation d, shape) and the insulator (dielectric) between the plates. It does NOT depend on the charge Q or the voltage V. For a parallel plate capacitor, C = epsilon_0 * A / d in air. A larger area or a smaller gap gives a larger capacitance.
One plate has +Q and the other has -Q, so the total charge is actually zero. By 'charge of the capacitor' we mean the magnitude Q on one plate. NCERT states this clearly: Q is the charge on one conductor, while the total charge of the capacitor is zero.
The capacitance of a parallel plate capacitor with air as medium is 6 uF. With the introduction of a dielectric medium, the capacitance becomes 30 uF. The permittivity of the medium is: (epsilon_0 = 8.85 x 10^-12 C^2 N^-1 m^-2)
If the plates of a parallel plate capacitor connected to a battery are moved close to each other, then: A. The charge stored in it increases. B. The energy stored in it decreases. C. Its capacitance increases. D. The ratio of charge to its potential remains the same. E. The product of charge and voltage increases. Choose the most appropriate answer.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
The defining formula is C = Q/V, where Q is the charge on one plate and V is the potential difference. For a parallel plate capacitor in air, C = epsilon_0 * A / d, where A is plate area and d is the gap.
The SI unit is the farad (F). 1 farad = 1 coulomb per volt (1 F = 1 C/V). Since 1 F is very large, practical values are in microfarad (uF) or picofarad (pF).
No. Capacitance depends only on the shape and size of the plates and the insulator between them. Q and V can change together, but their ratio C stays fixed for a given capacitor.
A capacitor with large C can store a large charge Q at a small voltage V. This lets circuits store energy and release it quickly, which is important in flash cameras, power supplies, and filters.
Yes. One plate carries +Q and the other carries -Q, so the net charge is zero. The value Q we quote is the magnitude on one plate.
