Question

9. Electrons pass through the parallel electrodes shown in FIGURE EX37.9 with a Speedtowards left . 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.

Short answer

and it is directed into the plane of paper.

Step-by-step solution

Given information

Voltage, Length, Width, Speed towards left.

conceptual understanding

Since the upper plate is at a higher potential so Electric field is in downward direction.

Since electron is going left and we need the resulting magnetic force to be in downward direction (opposite to electric field) so that net force is zero.

Using the right hand rule

we can see that magnetic field is directed into the plane of paper.

calculation

Electric field

Magnetic force on electron is given by where B is magnetic field.so now, on comparing magnitudes :-