State whether an alpha particle will experience any force in a magnetic field if (alpha particles are positively charged particles).
(i) it is placed in the field at rest.
(ii) it moves in the magnetic field parallel to field lines
(iii) it moves in the magnetic field perpendicular to field lines.
Justify your answer in each case.
Force acting a particle having charge q moving with velocity u in a magnetic field B is given by:
F = q uB sinθ
Where, θ is the angle between velocity o and magnetic field B.
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When alpha particle is rest i.e., u = 0, then,
F = 0 (No force) -
When alpha particle moves parallel to the magnetic field, 0 = 0°, then,
F = q uB sin 0° = 0 (No force) -
When alpha particle moves perpendicular to magnetic field, 0 = 90°, then,
F = q oB sin 90° = q oB (maximum force)