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A beam of electrons is moving with constant velocity in a region having simultaneous perpendicular electric and magnetic fields of strength 20 Vm-1 and 0.5 T respectively at right angles to the direction of motion of the electrons. Then the velocity of electrons must be
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- 8 m/s
- 20 m/s
- 40 m/s
- 1/40 m/s
Correct Option: C
The electron moves with constant velocity without deflection. Hence, force due to magnetic field is equal and opposite to force due to electric field.
| qvB = qE ⇒ v = | = | = 40 m/s | ||
| B | 0.5 |
