JEE Main 2015 · 4 Apr · Shift 1 · Physics Q14

← JEE Main 2015 · 4 Apr · Shift 1

PhysicsSingle correct+4 / -1Question 14 of 90

A long cylindrical shell carries positive surface charge σ in the upper half and negative surface charge −σ in the lower half. The electric field lines around the cylinder will look like figure given in :

(figures are schematic and not drawn to scale)

Dipole-like loops leaving the upper half and returning to the lower half

Cross-section of the cylinder (+ charges on the upper half, − on the lower half) with field lines: closed loops from the positive upper half round to the negative lower half, like a dipole field.

Lines radiating outward in all directions

Cross-section of the cylinder (+ charges on the upper half, − on the lower half) with field lines: straight radial lines all around.

Lines running horizontally past the cylinder, bending around it

Cross-section of the cylinder (+ charges on the upper half, − on the lower half) with field lines: lines from far left to far right bending around the cylinder.

Lines leaving the top and entering the bottom, with loops on both sides

Cross-section of the cylinder (+ charges on the upper half, − on the lower half) with field lines: many lines emerging upward from the top and loops curving down to the bottom on both sides.

Answer and worked solution

Official answer: A

Seen in cross-section, the cylinder is like a line dipole: field lines leave the positive upper half and curve round to end on the negative lower half, with no lines from far away. That is figure (1).

Topics:Electric field

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JEE Main 2015 · 4 Apr · Shift 1, Physics question 14