# Two coils 'P' and ' Q ' are separated by some distance.

Question:

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 ' $\mathrm{Q}$ '. 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:

1. (1) $6.67 \times 10^{-4} \mathrm{~Wb}$

2. (2) $3.67 \times 10^{-3} \mathrm{~Wb}$

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

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

Correct Option: 1

Solution:

(1) $Q_{\text {coil }}=(N Q) \propto i$

So, $\frac{Q_{1}}{Q_{2}}=\frac{i_{1}}{i_{2}}=\frac{3}{2}$

or $Q_{2}=\frac{2}{3} Q_{1}=\frac{2}{3} \times 10^{-3}=6.67 \times 10^{-4} \mathrm{~Wb}$