Question

Can someone give me the explanation of Q3?

Answer 1

Here,there is a positively charged particle is in West but it is deflected intonorth side by magnetic field.
We should find the direction of the magnetic field.
This is the explanation.

Answer 2

Hey mate,

here the direction of positively charged alpha particle is towards west this implies the direction of current is also towards west and the direction of magnetic force is towards north.

hence, according to Flemming's left hand rule the direction of magnetic field will be upward

INSHAALLAH IT WILL HELP YOU!