Question

A lot consists of 10 articles, 4 with minor defects, and 2 with major defects. One article is chosen at random. Find the probability in the following cases.[2] a) "The item has no defects. b) The item has no major defects.

Answer 1

Let A be the plate area and d be the distance between the plates,

1) A dielectric slab of thickness t is inserted,

Due to polarization inside the dielectric electric field will reduce,

So outside of dielectric, field = E₀

inside of dielectric, field = E = E₀/k

where k is the dielectric constant,

So the net potential will be,

V = Et + E₀(d-t)

=> V = E₀t/k + E₀(d-t)

=> V = E₀(d - t + t/k)

we know that, E₀ = q/ε₀A

=> V = q(d - t + t/k)/ε₀A

=> C = q/V

=> C = ε₀A/(d - t + t/k)

which is the required expression for capacitance,

2) A metallic plate of thickness t is inserted,

when a conducting metallic plate is inserted then electric field inside the plate will be zero

=> E = E₀/k = 0

=> k = ∞

hence putting the value of k in the above equation we get,

C = ε₀A/(d - t)

which is the required expression for capacitance with metallic plate