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Q. 9 - Excercises And Problems

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Physics for Scientists and Engineers: A Strategic Approach with Modern Physics
Found in: Page 1082

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Short Answer

Electrons pass through the parallel electrodes shown in FIGURE with a speed of . What magnetic field strength and direction will allow the electrons to pass through without being deflected? Assume that the magnetic field is confined to the region between the electrodes

The strength and direction of magnetic field is and out of page respectively.

See the step by step solution

Step by Step Solution

Step 1: Given Information

We are given that

speed of electron is ,

potential difference between two plates is and

distance d between two plates is .

We need to find magnetic field strength and direction that will allow the electrons to pass through without being deflected.

Step 2: Simplify

Applying Newton's law of motion in y direction, we get

m= -

where is acceleration of electron in y direction, is electric force and is magnetic force on electron

According to question, electrons are passing without being deflected,

therefore, = 0

Substituting value of in equation , we get,

0 =

On solving,

-

From the definition of and

and

where q is charge of electron, E is electric field , v is velocity of electron and B is magnetic field.

Substituting value of and in equation , we get

qE = qvB

On solving,

-

Expression for electric field between two plates is

-

substituting equation in equation , we get

-(5)

substituting the given values in equation (5), we get

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