Question

A plastic rod of length 2.2m and radius 3.6 mm carries a negative charge of `3.8xx10^(-7) C` spread uniformly over its surface. What is the electric field near the mid-point of the rod, at a point on its surface?

Answer 1

Here, l = 2.2m,
`r = 3.6 mm = 3.6xx10^(-3)m`.
`q = -3.8xx10^(-7)C.E = ?`
Linear charge density, `lambda = (q)/(1) = (-3.8xx10^(-7))/(2.2)`
`=-1.73xx10^(-7) Cm^(-1)`
As `E = (lambda)/(2pi in_(0) r) = (2 lambda)/(4pi in_(0) r)`
`:. E = (2(-1.73xx10^(-7)) xx9xx10^(9))/(3.6xx10^(-3))`
`= -8.6xx10^(5) N//C`