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Moving Charges and Magnetism — Physics STD 12 Science — Question

Bihar BoardEnglish MediumSTD 12 SciencePhysicsMoving Charges and Magnetism1 Mark
Question
Two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
  1. Both A and R are true and R is the correct explanation of A.
  2. Both A and R are true but R is NOT the correct explanation of A.
  3. A is true but R is false.
  4. A is false and R is also false.
Assertion (A): When force is zero, the charged particle follows linear path.
Reason (R): A charged particle enters in a uniform magnetic field, whose velocity makes an angle 8 with magnetic field will cover a linear path.
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Answer

  1. A is true but R is false.

Explanation:

When charged particle enters the uniform field they makes angle $\theta$ with the field. Then its path is decided by combined effect of two component of velocity. $\text{v}\cos\theta$ parallel to the field. Due to the parallel field the charge will follow a linear path and due to the perpendicular component $(\text{v}\cos\theta)$ of the field will be circular. This results in a helical path whose axis is parallel to the parallel component of the field.

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