Question
A uniform magnetic field is directed out of the page. A charged particle, moving in the plane of the page, follows a clockwise spiral of decreasing radius as shown. A reasonable explanation is
A uniform magnetic field is directed out of the page. A charged particle, moving in the plane of the page, follows a clockwise spiral of decreasing radius as shown. A reasonable explanation is
A.
the charge is positive and slowing down
B.
the charge is negative and slowing down
C.
the charge is positive and speeding up
D.
the charge is negative and speeding up
Answer :
the charge is positive and slowing down
Solution :
$$R = \frac{{mv}}{{qB}};\vec F = q\left( {\vec v \times \vec B} \right)$$
As $$R$$ decreases, $$v$$ will decrease.
Clockwise motion for upward magnetic field $$ \to + ve$$
$$R = \frac{{mv}}{{qB}};\vec F = q\left( {\vec v \times \vec B} \right)$$
As $$R$$ decreases, $$v$$ will decrease.
Clockwise motion for upward magnetic field $$ \to + ve$$