Question

11. A uniform magnetic field is directed into the
page. A charged particle, moving in the plane of
the page, follows a clockwise spiral of decreasing
radius as shown in the given figure. Which of
the following statements is correct?
(a) The charge is positive and slowing down.
o The charge is negative and slowing down.
(c) The charge is positive and speeding up.
fo) The charge is negative and speeding up.

Answer 1

Answer:

The charge is negative because qv×B determines the direction of acceleration.

F=qvB=

r

mv

2

.Thatis,v=

m

qB

R.

That is, v is proportional to R (the instantaneous radius of the spiral), since R is decreasing, so is v.

Hence, the charge is slowing down in speed.