NEET 2021 · PhysicsLoop centre fieldPrevious Year Question
A uniform conducting wire of length 12a and resistance 'R' is wound up as a current carrying coil in the shape of (i) an equilateral triangle of side 'a'. (ii) a square of side 'a'. The magnetic dipole moments of the coil in each case respectively are:
Answer: (C) √3 Ia² and 3 Ia². Answer: (C) Solution: Magnetic dipole moment m = N I A.
- A.3 Ia² and 4 Ia²
- B.4 Ia² and 3 Ia²
- C.√3 Ia² and 3 Ia²✓
- D.√3 Ia² and Ia²
Correct Answer
(C) √3 Ia² and 3 Ia²
Solution & Explanation
Answer: (C) Solution: Magnetic dipole moment m = N I A. Triangle: perimeter 3a, so number of turns N = 12a/(3a) = 4; area A = (√3/4)a². m₁ = N I A = 4 × I × (√3/4)a² = √3 I a². Square: perimeter 4a, so N = 12a/(4a) = 3; area A = a². m₂ = N I A = 3 × I × a² = 3 I a². Hence the moments are √3 Ia² and 3 Ia².
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