Q. A conduction rod of 1 m length and 1 kg mass is suspended by two vertical wires through its ends. An external magnetic field of 2 T is applied normal to the rod. Now the current to be passed through the rod so as to make the tension in the wires zero is $\left\lbrack Take\ g = 10\ {ms}^{- 2} \right\rbrack$
A) 0.5 A
B) 15 A
C) 5 A
D) 1.5 A
Explanation
(c) Magnetic force on the rod = $BIl$
Weight of the rod = $mg$
For no tension in wire, $BIl = mg$
or $I = \frac{mg}{Bl} = \frac{1 \times 10}{2 \times 1} = 5\ A$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.