Download Magnetic Forces on Moving Charges

Name: _______________________________
Magnetism Day 5
Date: _________
Period: _______
Electromagnetism
What determines the force on a moving charge in a magnetic field?
Write the equation for the force on a charged particle traveling through a magnetic field.
1. A proton moves at a speed of 1.2 x 106 m/s perpendicular to a constant magnetic
field of strength 0.004 T. What is the force on the proton?
2. In Figure P19.3, assume that vector v represents the velocity of a proton moving
through a uniform magnetic field and vector F represents the magnetic force
experienced by the proton. For each case, find the direction of the magnetic field
that will produce the magnetic force shown.
3. A duck flying horizontally due north at 15 m/s passes over Atlanta, where the
magnetic field of the Earth is 5 x 10-5 T in a direction 60‘ below a horizontal line
running north and south. The duck has a positive charge of 4.0 x 10-8 C.
a. What is the magnetic force acting on the duck?
b. What is the direction of the force?
4. A proton moves at a speed of 2.0 x 107 m/s at right angles to a magnetic field with
a magnitude of 0.10 T. Find the magnitude of the acceleration of the proton.
5. In the figure to the right, assume that the velocity
vector v shows the initial direction of motion of a
proton in a uniform magnetic field B. For each case
(expect E and F), find the direction of the magnetic
force acting on the proton.
6. Suppose an electron is chasing a proton up this page when suddenly a magnetic
field pointing into the page is applied. What would happen to the particles?
7. Why does the picture on a television screen become distorted when a magnet is
brought near the screen?
8. Can a stationary magnetic field set a resting electron in motion?
Now that we know this, how do we harness this force to make a
CRT (cathode ray tube) screen work to make a picture on your
TV?
Write the equation for centripetal force
Now write the equation for the force on a charged particle for the special case in which
Θ = 90‘, when it will move in a perfect circle.
Now set the two equations equal to each other:
Why do we want to calculate this?
Let’s try it.
9. An electron moves at a speed of 6.2 x 106 m/s perpendicular to a constant magnetic field.
The path is a circle of radius 2.2 x 10-3 m.
a. Draw a sketch showing the magnetic field and the electron’s path.
b. What is the magnitude of the field?
c. What is the magnitude of the electron’s acceleration?