Question

A particle having a charge of 10 microcoulomb and mass 1 microgram moves in a horizontal circle of radius 10 centimetre under the influence of magnetic field of 0.1 T .
when the particles at a point P a uniform electric field is switched on so that the particle starts moving along the tangent with uniform velocity the electric field is

Answer 1

For the particle to go undeflected,

qvBsinθ = qE


But E=vB--->1
mv^2 /r = qvB.

So
v=qBr/m---->2

From 1 and 2

E=q(B^2) ×r/m

Substituting all values in SI forms,

q=10×10^-6 C
B=0.1T
r=10×10^-6 m
m= 1×10^-9 KG

Se get E = 10V/m