A uniformly charged disk of radius 35.0 cm carries a charge density of 6.70 multiplied by 10-3 C/m2. Calculate the electric field on the axis of the disk at the following distances from the center of the disk.

Question

(a) 5.00 cm

Answer 1

Take the ring of the radius ‘r’ and the width ‘dr’ on the disc.
The electric field at the distance ‘x’ from the center of the disc is
dE=x•dq/4πε₀• {sqrt(r²+x²)}³,
where dq=σ•dA = σ•2•π•r•dr.
E(x)=
=intergral(limits: from 0 to R)
{σ•2•π•r•x•dr/ 4πε₀• [sqrt(r²+x²)]³ =
=(σx/2ε₀)•{(1/x)- [1/sqrt(R²+x²)]}.

Answer 2

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