Question

A rectangular loop of sides 10 cm and 5 cm carrying a current I of 12 A is placed in different
orientations as shown in the figures below:
If there is a uniform magnetic field of 0.3 T in the positive z direction, in which orientations the
loop would be in (i) stable equilibrium and (ii) unstable equilibrium?
(1) (1) and (3), respectively
(2) (2) and (4), respectively
(3) (2) and (3), respectively
(4) (1) and (2), respectively​

Answer 1

Answer

option (2) fig(2) and fig (4) respectively...

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we know that ....

T=IABsin∅. (where...T=torque )

I=12amp

A=(10×5)cm²=(10×5×10^-4) m²

B=0.3 tesla

now for ..fig(1)

T=12×(10×5×10^-4)×0.3

=1.8×10^-2 N.m(-y axis direction)

now for ..fig(2)

T=0 (stable equilibrium...as the direction of the force on each side is in outward direction)

now for ..fig(3)

T=12×(10×5×10^-4)×0.3

=1.8×10^-2 N.m(-x axis direction)

now for ..fig(4)

T=0 (unstable equilibrium...as the direction of the force on each side is in inward direction)

Hope This helps u....