Three identical coils C₁, C₂ and C₃ are closely placed such that they share a common axis. C₂ is exactly midway. C₁ carries current I in anti-clockwise direction while C₃ carries current I in clockwise direction. An induced current flows through C₂ will be in clockwise direction when (a) C₁ and C₃ move with equal speeds away from C₂ (b) C₁ moves towards C₂ and C₃ moves away from C₂ (c) C₁ and C₃ move with equal speeds towards C₂ (d) C₁ moves away from C₂ and C₃ moves towards C₂

Answer: (b). Viewed from one side, anticlockwise I in C₁ gives a field towards the viewer at C₂; clockwise I in C₃ gives a field away from the viewer. At the midpoint they cancel. (a) and (c): both changes are equal and opposite, so no net flux change and no current. (b): C₁ approaching increases the 'towards viewer' flux and C₃ receding reduces the 'away' flux; both increase net flux towards the viewer. Induced current in C₂ must give a field away from the viewer, i.e. clockwise. Answer (b).

Three identical coils C₁, C₂ and C₃ are closely placed such that they… | JEE Main 2026 (22 Jan, Shift 1)

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Lenz's Law, Eddy Currents & Induced Electric Field

Three identical coils $C_1, C_2$ and $C_3$ are closely placed such that they share a common axis. $C_2$ is exactly midway. $C_1$ carries current $I$ in anti-clockwise direction while $C_3$ carries current $I$ in clockwise direction. An induced current flows through $C_2$ will be in clockwise direction when

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Answer: (b)

Viewed from one side, anticlockwise $I$ in $C_1$ gives a field towards the viewer at $C_2$ ; clockwise $I$ in $C_3$ gives a field away from the viewer. At the midpoint they cancel.
(a) and (c): both changes are equal and opposite, so no net flux change and no current.
(b): $C_1$ approaching increases the 'towards viewer' flux and $C_3$ receding reduces the 'away' flux; both increase net flux towards the viewer.
Induced current in $C_2$ must give a field away from the viewer, i.e. clockwise. Answer (b).

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