PhysicsCBSE Class 12 · Sample paper, session 2023-24 · 1 mark · MCQ

CBSE Class 12 Physics sample paper 2023-24: question 2

From the official CBSE sample question paper for 2023-24, section A, question 2, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q2 · 1 mark · MCQElectric Charges and Fields

An electric dipole placed in an electric field of intensity $2 \times 1 0^{5}$ N/C at an angle of 30° experiences a torque equal to 4 Nm. The charge on the dipole of dipole length 2 cm is

(A)7 µC
(B)8 mC
(C)2 mC
(D)5 mC

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2023-24.

Hints

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

Hint 1

Recall the torque on a dipole in a uniform field.

Hint 2

Dipole moment is charge × dipole length; take length = 0.02 m.

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.

Torque $τ = pE sin θ = q (2 a) E sin θ$ , so $q = \frac{τ}{( 2 a ) E sin θ}$ .
½ mark
$q = \frac{4}{2 \times 1 0 ^{- 2} \times 2 \times 1 0 ^{5} \times sin 3 0 ^{\circ}} = \frac{4}{2000} = 2 \times 1 0^{- 3}$ C $= 2$ mC.
½ mark

Answer: 2 mC, option (C)

Where the marks are

Uses $τ = q (2 a) E sin θ$ (½ mark)
Gets $q = 2$ mC (½ mark)

Revise the chapter

Chapter: Electric Charges and Fields (notes, formulas, where marks are lost and every past question)
Topic: Electric Dipole

Practise this chapterBoard-style questions from Electric Charges and Fields, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2023-24: every question, by section.

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CBSE Class 12 Physics sample paper 2023-24: question 2

Hints

Step-by-step solution

Revise the chapter

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