Question

A positive charge is moving towards a person. The direction of magnetic field lines will be in:
A. Clockwise direction
B. Anticlockwise direction
C. Vertically upward direction
D. Vertically downward direction

Answer 1

Hint: In an electromagnetism, when a charged particle is moving without acceleration produces electric as well as magnetic field. The electric field is generated because of its nature and when it moves it generates a magnetic field too.

Complete answer:

Let us first understand the nature of magnetic field lines produced by an electric charge. The force on a positive charge is exactly the opposite direction to that of a negative charge. The direction of magnetic field lines due to a moving charge is always perpendicular to the plane formed by velocity direction and magnetic force.

Now, we can find the direction of magnetic field lines by pointing the right hand thumb in the direction of motion of a negatively charged particle, the curls of fingers give the direction of magnetic field lines. Since charge is moving towards the observer then pointing the thumb in the direction towards the observer the fingers will curl in anticlockwise direction so, for the observer, the direction of magnetic field line will be in anticlockwise direction.

Hence, the correct option is B.

Note: Remember, if a negative charge particle is moving towards the observer the direction of magnetic field lines would be in clockwise direction and also if this positive charge were going away from the observer, then direction of magnetic field line would be clockwise.