First slide

Electric flux

Question

A charge q is placed at some distance along the axis of a uniformly charged disc of surface charge density $σ$ . The flux due to the charge q through the disc is $ϕ$ . The electric force on charge q exerted by the disc is

Moderate

A

$σ ϕ$
B

$\frac{σ ϕ}{4 π}$
C

$\frac{σ ϕ}{2 π}$
D

$\frac{σ ϕ}{3 π}$

Solution

We know that if a point charge subtends a half-angle a on the circular cross-section of a disc, then flux passing through the disc is:
$ϕ = \frac{q}{2 ε_{o}} (1 - \cos α)$
Also, if a point charge q lies on the axis of a charged disc of charge density $σ$ and subtends a half-angle $α$ , then it experiences a force
$F = \frac{q σ}{2 ε_{o}} (1 - \cos α) = σ ϕ$

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