Sample 1Medium
A figure in the plane of the page shows a uniform magnetic field directed into the page, drawn as crosses. A proton enters the field moving towards the right. What is the direction of the magnetic force on the proton as it enters, and how does its path bend?
Show the answer
The answer is D.
F = q(v × B). With v to the right and B into the page, v × B points up the page, so the positive proton is pushed upward. Moving right and turning upward, it goes round in an anticlockwise circle.
- A.
Downward is the force on an electron, which carries negative charge.
- B.
The magnetic force is perpendicular to B, so it cannot point into the page.
- C.
An upward force on a particle moving right turns it anticlockwise, not clockwise.
NCERT: Class 12 Physics, Chapter 4