Question 173: Magnetism and Matter

Question

An electron is moving along +x direction with a velocity of 6 $$ 	imes $$ 106
 ms–1. It enters a region of uniform
electric field of 300 V/cm pointing along +y direction. The magnitude and direction of the magnetic
field set up in this region such that the electron keeps moving along the x direction will be :

Accepted Answer

$$\overrightarrow B $$ must be in +z axis.
$$\overrightarrow V  = 6 	imes {10^6}\widehat i$$
$$\overrightarrow E  = 300\widehat j$$ V/cm = 3 $$ 	imes $$ 10
4
$$\widehat j$$ V/m
$$\overrightarrow F $$ = $$q\overrightarrow E  + q\overrightarrow V  	imes \overrightarrow B $$
$$ 	herefore $$ $$q\overrightarrow E  + q\overrightarrow V  	imes \overrightarrow B $$ = 0
$$ \Rightarrow $$qE = qVB
$$ \Rightarrow $$ B = $${E \over V}$$ = $${{3 	imes {{10}^4}} \over {6 	imes {{10}^6}}}$$ = 5 $$ 	imes $$ 10
Ã¢ÂÂ3
T

Answer

3 $$ 	imes $$ 10–4 T, along –z direction

Answer

5 $$ 	imes $$ 10–3 T, along –z direction

Answer

5 $$ 	imes $$ 10–3 T, along +z direction

Answer

3 $$ 	imes $$ 10–4 T, along +z direction

Magnetism and Matter

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