Electrostatic Potential and Capacitance - Result Question 43

45. A parallel plate condenser with oil between the plates (dielectric constant of oil K=2 ) has a capacitance C. If the oil is removed, then capacitance of the capacitor becomes

(a) 2C

(b) 2C

(c) C2

(d) C2

[1999, 97]

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Answer:

Correct Answer: 45. (d)

Solution:

  1. (d) When oil is placed between space of plates

C=2Aε0d (1) [C=KAε0d., if .K=2]

When oil is removed C=Aε0d

On comparing both equations, we get C1=C/2

When dielectric is partially filled between the plates of a parallel plate capacitor then its capacitance increases but potential difference decreases. To maintain the capacitance and potential difference of capacitor as before separatoin betweeen the plates has to be increased by d. In such case

k=ttd (Here, t= seperation between plates.) 



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