Question

A combination of two conducting bodies separated by insulator can store electric charge

1. The above device is called………

2. Derive on expression for capacitance of the device with air as medium.

3. If mica of dielectric constant Ks placed between the plates. What are its advantages? Explain action of mica in the case.

Answer 1

1. capacitor. 

2. 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. 

• When mica sheet is introduced, capacitance of capacitor increases
• Mica sheet will prevent electric breakdown.