Question

A proton with a velocity in the positive x-direction enters a region where there is a uniform magnetic field B in the positive y-direction. You want to balance the magnetic force with an electric force so that the proton will continue along a straight line.

The electric field should be in the:

a)neg y direction

b)neg x direction

c)postive x direction

d)postive z direction

e)negative z

Answer 1

Positive z direction.

Step-by-step explanation:

The magnetic force acting on the electron is given by the formula as :

`F=q(v* B)`

q is the charge on proton

v is the speed of proton

B is the magnetic field

It is mentioned that the proton is moving with a velocity in the positive x-direction. The uniform magnetic field B in the positive y-direction such taht,

q = +e

v = vi

B = Bj

`F=e(v\ i* B\ j)`

Since,
`i* j=k`

`F=(evB)\ k`

So, the magnetic force acting on the proton in positive z axis. Hence, the correct option is (d) "positive z direction".