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Question
A charge ‘q’ moving along the X- axis with a velocity `vecv` is subjected to a uniform magnetic field B along the Z-axis as it crosses the origin O.
(i) Trace its trajectory.
(ii) Does the charge gain kinetic energy as it enters the magnetic field? Justify your answer.
Solution
(i)
The direction of magnetic field is along the negative X-direction. Hence, the magnetic force will act in such a way that this particle describes a circular motion as shown below.
(ii) No, the charge does not gain kinetic energy because the force and velocity are perpendicular to each other.
`W = vecF.vecv =Fvcostheta`
`theta = 90°`
Thus, force does not bring out any change in the velocity.
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