Maharashtra BoardEnglish MediumSTD 12 SciencePhysicsQuestion Bank [ 2022 ]2 Marks
Question
Explain "Magnetic force never does any work on moving charges".
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Answer
i. Magnetic force is given by $\overrightarrow{ F }_{ m }= q (\overrightarrow{ v } \times \overrightarrow{ B })$. ii. This makes direction of magnetic force $\left(\overrightarrow{ F }_{ m }\right)$ perpendicular to direction of velocity of charged particles $(\overrightarrow{ v })$. iii. Thus, the magnetic force is in turn perpendicular to the displacement of charged particles. iv. According to properties of the dot product, $\overrightarrow{ F }_{ m } \cdot \overrightarrow{ v }=0$, for any magnetic field $\overrightarrow{ B }$. Hence, magnetic force never does any work on moving charges.
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