Multiple choice

A dielectric slab of thickness 4 mm is placed between the plates of a parallel plate condenser. When the distance between the plates is increased by 3.5 mm, then the capacity of the condenser remains same. Find the dielectric of the medium.

  1. 8

  2. 30 x 10-6

  3. 2 x 10-6

  4. 1.87

  5. 12.5 x 10-2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Initially the capacity, 

C1 = єoA/d Let the distance is increased by x. When a slab of thickness d is introduced, then capacity C2 =  єoA/ (x+d/єr) since C1 = C2 Therefore, єoA/d = єoA/ (x + d/єr) Or d = (x+d/єr) єr = d/(d – x)     = 4 x10-3/(4 x10-3 – 3.5 x10-3)     = 4/0.5 = 8

Keep practicing — related questions