Question

3. If you curl the fingers of your right hand as shown, are the electric fluxes in FIGURE Q31.3 positive or negative?

Short answer

Part (a) The flux is negative.

Part (b) The flux is positive.

Step-by-step solution

Step 1. Introduction

Curl the right hand fingers around the loop with the thumb perpendicular to the surface of the loop. The thumb defines the positive direction.

If the electric field is directed along the direction of thumb then the flux through the surface is positive. If the electric field is directed opposite to the direction of thumb then the flux is negative.

Part (a)

In figure (a),

Curl the right hand fingers around the loop the thumb is directed out of the page, and electric field is directed into the page. So, the flux is negative.

Part (b)

In figure (b),

Curl the right hand fingers around the loop the thumb direction is left side, and electric field directed towards the left. So, the flux is positive.