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Home » Answer the following questions: (a) A magnetic field that varies in magnitude from point to point but has a constant direction (east to west) is set up in a chamber. A charged particle enters the chamber and travels undeflected along a straight path with constant speed. What can you say about the initial velocity of the particle? (b) A charged particle enters an environment of a strong and non-uniform magnetic field varying from point to point both in magnitude and direction and comes out of it following a complicated trajectory. Would its final speed equal the initial speed if it suffered no collisions with the environment?
Answer the following questions: (a) A magnetic field that varies in magnitude from point to point but has a constant direction (east to west) is set up in a chamber. A charged particle enters the chamber and travels undeflected along a straight path with constant speed. What can you say about the initial velocity of the particle? (b) A charged particle enters an environment of a strong and non-uniform magnetic field varying from point to point both in magnitude and direction and comes out of it following a complicated trajectory. Would its final speed equal the initial speed if it suffered no collisions with the environment?
Class 12 | Moving Charges and Magnetism | NCERT | Physics
Answer the following questions: (a) A magnetic field that varies in magnitude from point to point but has a constant direction (east to west) is set up in a chamber. A charged particle enters the chamber and travels undeflected along a straight path with constant speed. What can you say about the initial velocity of the particle? (b) A charged particle enters an environment of a strong and non-uniform magnetic field varying from point to point both in magnitude and direction and comes out of it following a complicated trajectory. Would its final speed equal the initial speed if it suffered no collisions with the environment?

(a) The force acting on a charged particle, moving in a magnetic field is given by

F = q v B sinθ 

now, if no force acts on the charged particle, it will proceed along a straight path at a constant speed in a magnetic field. It implies that F = 0. And we know that It will be possible only if

sinθ = 0

This in turn implies that the angle theta is either zero or 180 degrees. It signifies that a charged particle’s initial velocity v is either parallel or antiparallel to the magnetic field B.

(b) Yes, since the magnetic force acting on a charged particle traveling in a magnetic field can change the direction of v rather than the magnitude of it.

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