A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength 20 V m⁻¹ and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons?

Question

Accepted Answer

(4) 40 m s⁻¹. Given: E=20 V m⁻¹ and B=0.5 T, both perpendicular to the motion and to each other. Idea: constant velocity means zero net force, so the electric and magnetic forces must cancel — a velocity selector. qE=qvB. The charge cancels, so the answer is the same for any particle. v=E/B. v=(20)/(0.5). v=40 m s⁻¹.

A beam of electrons is moving with constant velocity in a region having electric and magnetic fields of strength 20 V m⁻¹ and 0.5 T at right angles to the direction of motion of the electrons. What is the velocity of the electrons?

Step-by-step solution

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