Electrostatics Question 48

Question: The plates of parallel plate capacitor are charged upto100 V . A2mm thick plate is inserted between the plates. Then to maintain the same potential difference, the distance between the plates is increased by1.6 mm . The dielectric constant of the plate is [MP PMT 1991]

Options:

A) 5

B) 1.25

C) 4

D) 2.5

Show Answer

Answer:

Correct Answer: A

Solution:

In air the potential difference between the plates

Vair=σε0.d ….. (i)

In the presence of partially filled medium potential difference between the plates Vm=σε0(dt+tK) ….. (ii) Potential difference between the plates with dielectric medium and increased distance is Vm=σε0(d+d)t+tK ….. (iii)

According to question Vair=Vm which gives K=ttd Hence K=221.6=5



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