Two coils P and Q are separated by some distance. When a current of 3 A flows through coil P a magnetic flux of $10^{-3} \mathrm{~Wb}$ passes through Q. No current is passed through Q. When no current passes through P and a current of 2 A passes through Q, the flux through P is:

(B) $6.67 \times 10^{-4} \mathrm{~Wb}$

(A) $6.67 \times 10^{-3} \mathrm{~Wb}$

(C) $3.67 \times 10^{-4} \mathrm{~Wb}$

(D) $3.67 \times 10^{-3} \mathrm{~Wb}$

JEE Main · 2019 · 09 Apr 2019 · Shift 2 · Electromagnetic Induction

Two coils P and Q are separated by some distance. When a current of 3 A flows through coil P a magnetic flux of

1 0^{- 3} Wb

passes through Q. No current is passed through Q. When no current passes through P and a current of 2 A passes through Q, the flux through P is:

(A) $6.67 \times 1 0^{- 3} Wb$
(B) $6.67 \times 1 0^{- 4} Wb$ ✓ Correct
(C) $3.67 \times 1 0^{- 4} Wb$
(D) $3.67 \times 1 0^{- 3} Wb$

Answer: (B)

Solution

Mutual inductance works both ways through the same coefficient,

M_{P Q} = M_{QP} = M

. From the first situation,

3

A in P links a flux of

1 0^{- 3}

Wb through Q, so

M = \frac{1 0 ^{- 3}}{3}

H. Turning it around,

2

A flowing in Q links P with

ϕ_{P} = M \times 2 = \frac{2}{3} \times 1 0^{- 3} = 6.67 \times 1 0^{- 4}

Wb.

JEE Main · 2019 · 09 Apr 2019 · Shift 2 · Single correct option

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