00:01
Student in this problem we have an electron traveling between two plates to charged plates the velocity of the electron is 1 .7 into 10 to the per 7 meter per second now the plates are charged with a battery of 220 volt and the separation between the plates is 1 semi now we are asked what is the magnet direction of the magnetic field we should apply so that the electron doesn't deflect from its path now due to this plate the electron will experience a force along this direction if this is the positive plate then the electron will experience a force along this direction and the force will be let's name it by f e force will be q times e where q is the charge of the electron and is the electric field.
01:47
Now the electric field we can calculate by 220 volts.
01:52
So voltage divided by the separation which is one semi 1 into 10 to the minus 2.
01:58
So newton per coulum.
02:02
So 22 into 10 to the power 3, newton per column.
02:10
So now if we don't want the electron to get deflected, then we have to apply a mass.
02:16
Magnetic field we have to counter effect the force fe by applying another force on this direction exactly opposite direction so let's say this is fb now if i apply a magnetic field the force that the electron will experience will be fv equals to qv cross b where v is the velocity of the electron and b is the magnetic field now this force has to be equal to f e q.
02:55
Now let's assume that b is perpendicular to v.
02:58
So this will be qvv sine 90 which is 1...