Given parameters are:

Number of turns n=500

area A = 4cm2 = 4×10−4m2

resistance R = 500Ω

magnetic field B = 0.2wb/m2

We have to calculate the amount of charge flowing through the coil.

Magnetic flux is given by the following formula.

ϕ = nBAcosθ

Where n is a number of turns, B is a magnetic field, A is the area, and θ is the angle between the area vector and the magnetic field.

So, let us calculate the change in magnetic flux when it is turned over (rotated by 180 -degrees).

△ϕ=nBAcos0−(nBAcos180)

Let us simplify the expression.

△ϕ = nBA + nBA = 2nBA = 2 × 500 × 0.2 × 4 × 10−4

△ϕ = 8×10−2

The charge flowing through the area is given by the following formula.

△Q = △ϕ/resistance = 8×10−2/500 =1.6×10−4C **=0.16×10−3C**