JEE Main · 2021 · 25 Jul 2021 · Shift 2 · Magnetic Effects of Current

Two ions having same mass have charges in the ratio

1 : 2

. They are projected normally in a uniform magnetic field with their speeds in the ratio

2 : 3

. The ratio of the radii of their circular trajectories is :

(A) $3 : 1$
(B) $2 : 3$
(C) $4 : 3$ ✓ Correct
(D) $1 : 4$

Answer: (C)

Solution

The radius of circular motion in a magnetic field is

r = \frac{m v}{q B}

. Given

m_{1} = m_{2}

q_{1} : q_{2} = 1 : 2

, and

v_{1} : v_{2} = 2 : 3

, we have

\frac{r _{1}}{r _{2}} = \frac{m _{1}}{m _{2}} \cdot \frac{v _{1}}{v _{2}} \cdot \frac{q _{2}}{q _{1}} = 1 \cdot \frac{2}{3} \cdot 2 = \frac{4}{3}

JEE Main · 2021 · 25 Jul 2021 · Shift 2 · Single correct option

Practise more: all JEE Main PYQs on Magnetic Effects of Current →

More JEE Main questions on Magnetic Effects of Current

An infinitely long straight wire carrying current I is bent in a planer shape as shown in the diagram. The radius of the circular part is r . The magnetic field at the centre O of the circular loop is :
JEE Main 2026View solution →
The current passing through a conducting loop in the form of equilateral triangle of side $43 cm$ is 2A. The magnetic field at its centroid is $α \times 1 0^{- 5} T$ . The value of $α$ is ____.
(Given : …
JEE Main 2026View solution →
Three long straight wires carrying current are arranged mutually parallel as shown in the figure. The force experienced by 15 cm length of wire $Q$ is ______.
( $μ_{0} = 4 π \times 1 0^{- 7} T . m / A$ )
JEE Main 2026View solution →
The magnetic field at the centre of a current carrying circular loop of radius $R$ is $16 μ T$ . The magnetic field at a distance $x = 3 R$ on its axis from the centre is ____ $μ T$ .
JEE Main 2026View solution →
Two identical circular loops P and Q each of radius r are lying in parallel planes such that they have common axis. The current through P and Q are I and 4I respectively in clockwise direction as seen from O. The net magnetic field at O is:
JEE Main 2026View solution →
A long cylindrical conductor with large cross section carries an electric current distributed uniformly over its cross-section. Magnetic field due to this current is :
A. maximum at either ends of the conductor and minimum at the midpoint
B. maximum at the axis of the conductor
C …
JEE Main 2026View solution →