1. one use of capacitor:
- Capacitor is used to store electric charges
- It is used to prevent dc current.
2. Expression for capacitance of a capacitor: Potential difference between two plates V = Ed
= \(\frac{\sigma}{\varepsilon_0}d\) (∴\(E=\frac{\sigma}{\varepsilon_0}\))
V = \(\frac{Q}{A\varepsilon_0}d\) ..........(1) \((σ=\frac{Q}{A})\)
Capacitance C of the parallel plate capacitor,
C = \(\frac{Q}{V}\) ...........(2)
Sub eq. (1) in eq. (2)
C = \(\frac{Q}{\frac{Q}{A\varepsilon_0}d}\)
C = \(\frac{A\varepsilon_0}{d}\)
3. C = 10µF
When dielectric slab is placed, New capacitance
C1 = KC
10 × 10-6 = 2 × C, C = 5 × 10-6 F.