SP 212 Worksheet
Lesson 20: Ch. 28.4 & 28.6, Magnetic Forces on Charges & Currents
1) An alpha particle ( q = +2 e , m = 4 .
00 m p
) travels in a circular path of radius 3 .
8 cm in a uniform magnetic field of magnitude 1 .
0 T. Calculate (a) its speed, (b) its period of revolution, (c) its kinetic energy, and (d) the electric potential difference across which is would need to be accelerated to achieve this energy.
2) A wire of mass m and length L is suspended by a pair of conducting springs in a uniform magnetic field of magnitude B (directed into the page). What is the magnitude and direction of the current required to remove the tension in the springs ( F spring
= 0)? Give your answer in terms of m , L , B , and g .
3) A wire of length 2 .
56 m is parallel with the x -axis. It carries a 14 .
9 A current in the + x direction. A uniform magnetic field of magnitude B = 2 .
10 T lies in the x y plane, and is oriented 49 .
3
◦ above the x -axis.
What is the magnitude and direction of the magnetic force that acts on the wire?