Skip to content

Write the nature of… (Class 12 Physics SQP 2026-27, Q18)

questionbuddy.in/q/cbse-12-physics-2026-27-sqp-q18-nature-path-free-electrons-conductor

PhysicsCBSE Class 12 · Sample paper, session 2026-27 · 2 marks · Very short answer

CBSE Class 12 Physics sample paper 2026-27: question 18

From the official CBSE sample question paper for 2026-27, section B, question 18, for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q18 · 2 marks · Very short answerCurrent Electricity

Write the nature of path of free electrons in a conductor in the

a) presence of electric field,
b) absence of electric field.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

Open one hint at a time and try again before the next.

Hint 1

Think of electrons as gas molecules colliding with the fixed ions.

Hint 2

What extra force acts on an electron between collisions when a field is applied, and in which direction?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) With an electric field: each free electron still moves randomly between collisions, but between collisions it is accelerated opposite to . Its path becomes a curved zig-zag path with a slow net drift opposite to the field (drift velocity), which constitutes the current.

    1 mark

  2. (b) Without an electric field: free electrons move randomly in straight lines between collisions with the ions due to thermal energy, changing direction at each collision; the path is a random zig-zag, the average velocity is zero, so there is no net flow and no current.

    1 mark

Answer: (a) Curved zig-zag path with net drift opposite to E; (b) random straight-line zig-zag path with zero net displacement (no current).

Where the marks are

  • Presence of field: zig-zag (curved) path with net drift opposite to field (1 mark)
  • Absence of field: random zig-zag straight-line paths, zero average velocity, no current (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Current Electricity, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.