Magnetic Effects Of Current Question 13
Question 13 - 30 January - Shift 1
A massless square loop, of wire of resistance $10 \Omega$. supporting a mass of I g. hangs vertically with one of its sides in a uniform magnetic field of $10^{3} G$, directed outwards in the shaded region. A dc voltage $V$ is applied to the loop. For what value of $V$. the magnetic force will exactly balance the weight of the supporting mass of $1 g$ ?
(If sides of the loop $=10 cm, g=10 ms^{-2}$ )
(1) $\frac{1}{10} V$
(2) $100 V$
(3) $1 V$
(4) $10 V$
Show Answer
Answer: (4)
Solution:
Formula: Magnetic Field Due To Infinite Straight Wire
$F_m=mg$
$\therefore \quad ILB=mg$
$\therefore(\frac{V}{R}) LB=mg$
$\therefore V=\frac{mgR}{LB}$
$=\frac{(1 \times 10^{-3} kg)(10 m / s^{2})(10 \Omega)}{(0.1 m)(10^{3} \times 10^{-4} T)}=10 V$
