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Moving Charges and Magnetism — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsMoving Charges and Magnetism2 Marks
Question
Write the relation for the forces $\overrightarrow{F}$ acting on a charge carrier q moving with a velocity $\overrightarrow{V}$ through a magnetic field $\overrightarrow{B}$ in vector notation. Using this relation, deduce the conditions under which this force will be (1) maximum (2) minimum.
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Answer

$\stackrel\rightharpoonup{\text{F}} = \text{q}\big(\stackrel\rightharpoonup{V}\times\stackrel\rightharpoonup{B}\big)$ $\therefore |\stackrel\rightharpoonup{\text{F}}| = \text{qVB}sin\theta$
  1. Maximum when
$\stackrel\rightharpoonup{\text{V}}\bot\stackrel\rightharpoonup{\text{B}}$ Or $\theta = \pi/2$
  1. Minimum when
$\stackrel\rightharpoonup{\text{V}}||\stackrel\rightharpoonup{\text{B}} $ Or $\theta = 0 $ Or $180^{\circ}$

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