Question

Two point charges each of $10\mu C$ are projected in a magnetic field B. First particle is projected with velocity 2 m/s along magnetic field while second particle is projected at $4\mathring{5}$ with magnetic field with velocity 5 m/s. The path of motion of charges will be

• A. straight line and circular respectively
• B. straight line and helical respectively
• C. circular and helical respectively
• D. parabolic and helical respectively

Answer 1

The correct option is B straight line and helical respectively

Given

Two charges of charge 10C

Velocity of particle 1 is 2 m/s

Angle with Magnetic field is 0

Velocity of particle 2 is 5 m/s

Angle with magnetic field is 45

Solution

To know path of charge in magnetic field we need know the force on that particle because of magnetic field.

Force on charge is qvBsin$\theta$

Foe particle 1 sin is 0 therefore force is 0

hence its path will be straight line

In particle 2 Force on charge will be qvBsin45

here there will be two components of v that is one will be vsin$\theta$ which will cause circular motion and one will be vcos$\theta$ which will cause straight line motion. combining both motions we will get helical motion.

THe correct option is B