First slide

Electric field

Question

Two concentric rings, one of radius R and total charge +Q and the second of radius 2R and total charge -✓8Q, lie in x-y plane (i.e., z = 0 plane). The common centre of rings
lies at origin and the common axis coincides with z-axis. The charge is uniformly distributed on both the rings. At what distance from origin is the net electric field on z-axis zero?

Moderate

A

$\frac{R}{2}$
B

$\frac{R}{\sqrt{2}}$
C

$\frac{R}{2 \sqrt{2}}$
D

$\sqrt{2} R$

Solution

Electric field at a point on z-axis distant r from origin is
$E = \frac{1}{4 {πε}_{0}} (\frac{Qr}{{(r^{2} + R^{2})}^{3 / 2}} - \frac{\sqrt{8} Qr}{{(r^{2} + 4 R^{2})}^{3 / 2}}) = 0 Solving, we get r = \sqrt{2} R$

Get Instant Solutions

When in doubt download our app. Now available Google Play Store- Doubts App

Recieve an sms with download link

Doubts App

OR

SCAN ME

Doubts App

Doubts App