http://postimg.org/image/8emyaju6n/ Can someone help explain this problem to me?
ID: 1380311 • Letter: H
Question
http://postimg.org/image/8emyaju6n/
Can someone help explain this problem to me?
A uniform magnetic field of magnitude .8 T in the negative z-direction is present in a region of space, as shown in the figure. A uniform electric field is also present. A proton (positive charge) that is projected with an initial velocity v0 = 10^4 m/s in the positive x-direction passes through the region without deflection (magnetic force equals electric force Fb=Fe). What is the electric field vector in the region?
Correct answer is 8000V/m, in the negative y-direction
Explanation / Answer
magnetic force, FB = q*( v cross B)
= q*vo*B*sin(90)
= q*vo*B (towards +y direction)
Fnet = 0
FB - Fe = 0
FB = Fe
q*vo*B = q*E
E = Vo*B
= 10^4*0.8
= 8000 V/m
Here magnetic force acts in +y direction. so, Electric forc should act towards -y axis.
so, direction of E should be towards -y axis.
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