A straight horizontal conduction rod of length 0.45 m and mass 60 g is suspended by two vertical wires at its ends. A current of 5.0 A is set up in the rod through the wires. (a) What magnetic field should be set up normal to the conductor in order that the tension in the wires is zero? (b) What will be the total tension in the wires if the direction of current is reversed keeping the magnetic field same as before? [Ignore the mass of the wires.] g = 9.8 m s − 2

Question

A straight horizontal conduction rod of length 0.45 m and mass 60 g is suspended by two vertical wires at its ends. A current of 5.0 A is set up in the rod through the wires. (a) What magnetic field should be set up normal to the conductor in order that the tension in the wires is zero? (b) What will be the total tension in the wires if the direction of current is reversed keeping the magnetic field same as before? [Ignore the mass of the wires.] g = 9.8 m s − 2,

MARKS App · Accepted Answer

At balance tension in the strings and magnetic force I Bl balance the weight of wire. $ 2 T + I Bl = m g ( a ) F or t e n s i o nin t h e w i re t o b ezero . I B I ​ = m g ⇒ B = I l m g ​ = 5 × 0.45 60 × 1 0 − 3 × 9.8 ​ = 0.26 T ​ ( b ) I f t h e d i rec t i o n o f c u rre n t i s n o w re v erse d , k ee p in g t h ec u rre n t an d ma g n e t i c f i e l d s am e , t h e n 2 T = I Bl + m g 2 T=2 m g=2 	imes 60 	imes 10^{-3} 	imes 9.8 T o t a lt e n s i o n =1.176 \mathrm{~N}$

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