Question

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in Figure. In the field, an electron and a proton move as shown. The electron and the proton experience 

(a) forces both pointing into the plane of the paper 

(b) forces both pointing out of the plane of the paper 

(c) forces pointing into the plane of the paper and out of the plane of the paper, respectively 

(d) force pointing opposite and along the direction of the uniform magnetic field respectively

Answer 1

The answer is (a) forces both pointing into the plane of paper

• Direction of movement of electron is opposite to the direction of electric current.
• This will make the current move upwards. 
• If index finger shows direction of magnetic field, ring finger shows current direction and direction of thumb into paper.