Question

Figure shows an electric field extending over three regions, labeled I, II, and III. Answer the following questions. (a) Are there any isolated charges? If so, in what region and what are their signs? (b) Where is the field strongest? (c) Where is it weakest? (d) Where is the field the most uniform?

Short answer

(a) Yes, positive charge exists in region II. (b) The field is strongest in region II. (c) The field is weakest in region III. (d) The field is most uniform in region I.

Step-by-step solution

Electric field lines

The force acting on unit positive test charge is known as electric field. The direction of the electric field is given by imaginary field lines known as electric field lines. The electric field lines are directed from positive to the negative charge.

The strength of the electric field is determined by the density of lines (lines per unit area). Greater the line density, stronger the field will be.

(a) Presence of isolated charge

The electric field lines do not intersect each other. In region II, the electric field lines bents inwards from all direction. This is the sign of the presence of isolated positive charge.

(b) Strongest field

Electric field strength is strongest where the electric lines are closest.

Hence, the strength of electric field is strongest in region II.

(c) Weakest field

Electric field strength is weakest where the electric field lines are farthest.

Hence, the strength of electric field is weakest in region III.

(d) Uniform field

The field is uniform in region I because the field lines are at uniform separation throughout the region.