An electron enters a uniform magnetic field with the same speed in two trials

PHYSICS · Single correct · AP · Physics 2: Algebra-based · Magnetism and Electromagnetism · Magnetism and Electromagnetism

Problem

An electron enters a uniform magnetic field

\vec B

with the same speed

v

in two trials. In trial 1 the angle between

\vec v

and

\vec B

30^{\circ}

, while in trial 2 it is

60^{\circ}

. Let

r_1,\,p_1

be the radius and pitch of the helix in trial 1, and

r_2,\,p_2

the corresponding quantities in trial 2. Which statement about

r_2

and

p_2

relative to

r_1

and

p_1

is correct? (a)

r_2>r_1

and

p_2>p_1

(b)

r_2<r_1

and

p_2>p_1

(c)

r_2>r_1

and

p_2<p_1

(d)

r_2>r_1

and

p_2=p_1