Question

1. The Coulomb force between two charges q1 and q2 at separation r in air is F. If half of the separation is filled with medium of dielectric constant 9, what will be the value of new coulomb force? 2.There are two large parallel metallic platesP1 and P2 carrying surface charge densities σ1 and σ2(σ1> σ2) respectively, placed at some distance d apart in vacuum. Determine the work done by the electric field in moving a point charge q from P1 to P2 along a line a (a

Answer 1

Answer:

Explanation:

1 )

F = k q₁q₂ / r² where k = 9 x 10⁹

So force F₁ =  $\frac{kq_1q_2}{(\frac{r}{2}+\frac{\sqrt{9} r}{2})^2 }$

= $\frac{kq_1q_2}{(\frac{r}{2}+\frac{3 r}{2} )^2 }$

= k q₁q₂ /4 r²

F₁  =  F / 4

2 ) Electric field due to charge density σ

= σ / ε₀

So net electric field between the plates

=   ( σ₁ - σ₂ )  / ε₀

Force on charge  q

=  ( σ₁ - σ₂ ) q   / ε₀

work done = force x displacement

=  ( σ₁ - σ₂ ) x q x d   / ε₀