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Magnetism
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Niteesh Mehra
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Joined: 28 Oct 2007
Posts: 207
25 Dec 2007 23:48:42 IST
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the question is not clear dude..Wat u can do is equate 10x10^3=1/2 mv^2 or r=sq.rt(2mKE)/qB
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5 Jan 2008 01:33:16 IST
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heres how you do it:
KE of the electron is given, so use the equation KE = 1/2mv2
and get v. This will be the horizontal component of the velocity of the electron, which will remain unchanged during the course of its motion, as the magnetic field is perpendicular (should be, though its not mentioned) to the motion of the electron.
Now, the magnetic field will exert a force of Bqv on the electron which will produce an acceleration which has the magnitude Bqv/m.
Then use kinematics equation, ie, s = ut + 1/2at2
Here u=0.
So, S = 1/2at2
To get t : it is simply 1m divided by the horizontal component of velocity calculated in the first part.
Note mass of electron = 9.31 x 10-31kgs
Substitute the values, get the answer. Get back if you have doubts
KE of the electron is given, so use the equation KE = 1/2mv2
and get v. This will be the horizontal component of the velocity of the electron, which will remain unchanged during the course of its motion, as the magnetic field is perpendicular (should be, though its not mentioned) to the motion of the electron.
Now, the magnetic field will exert a force of Bqv on the electron which will produce an acceleration which has the magnitude Bqv/m.
Then use kinematics equation, ie, s = ut + 1/2at2
Here u=0.
So, S = 1/2at2
To get t : it is simply 1m divided by the horizontal component of velocity calculated in the first part.
Note mass of electron = 9.31 x 10-31kgs
Substitute the values, get the answer. Get back if you have doubts











