Question

An aluminium ring $B$ faces an electromagnet $A$. The current $I$ through $A$ can be altered,

• A. if $i$ increase, $A$ will repel $B$
• B. if $i$ increase, $A$ will attract $B$
• C. if $i$ increase, $B$ will repel $A$
• D. whether $i$ increase or decrease, $B$ will not experience any force

Answer 1

Answer: (A)

If current is passed through solenoid $A$ as shown. Current entering at end $A$ is clockwise. When seen from the side of $A$, so it develops south polarity at $A$ and north polarity at $B$. When current $l$ through $A$ increase, it is like north of the magnet approaching the ring $B$ and due to Lenz's law face of ring $B$ facing $B$ develops north polarity and hence there is repulsion between the two.