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A uniform magnetic field B is confined to a cylindrical region and is increasing at a constant rate. An electron is placed at a point P outside (or at the edge of) this region. What is the instantaneous acceleration of the electron at P due to the induced field?
- non-zero, tangential (perpendicular to the radius through P)
- zero
- radially towards the axis
- radially away from the axis
Correct answer: non-zero, tangential (perpendicular to the radius through P)
Solution
A time-varying magnetic field induces a circulating electric field along concentric circles. At P this induced E is tangential, so the electron experiences a force (and acceleration) perpendicular to the radial line joining P to the axis; it is not zero.
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