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Question: A uniform magnetic field acts at right angles to the direction of motion of electrons. As a result, ...

A uniform magnetic field acts at right angles to the direction of motion of electrons. As a result, the electron moves in a circular path of radius 2 cm. If the speed of the electrons is doubled, then the radius of the circular path will be

A

2.0 cm

B

0.5 cm

C

4.0 cm

D

1.0 cm

Answer

4.0 cm

Explanation

Solution

r=mvqB⇒r∝v,⇒r2=2r1=2×2=4 cmr = \frac { m v } { q B } \Rightarrow r \propto v , \Rightarrow r _ { 2 } = 2 r _ { 1 } = 2 \times 2 = 4 \mathrm {~cm}