Physics 106, Summer 2012
19 Sec. 6-10
Did you complete the reading assignment?
Did you complete the entire quiz or spend at least 15
minutes working on this quiz and the attached links?
1) A magnetic force is
created when a charge or a charged object is moving through a magnetic
2) A magnetic field is induced by a
current carrying wire.
3) The direction of magnetic forces and
fields are determined by the right hand rule.
magnetism cannot accurately
be separated into to distinct entities. They are actually the same, manifested
in different ways. To be accurate in your description of them, you really need
to combine them and call it electromagnetism. That is why when a charge moves
through a magnetic field it experiences a magnetic force. It is also why when
current is moving through a wire it creates a magnetic field around the wire.
Go to the following applet:
and click on the black box to start it.
The Xs and Os show the direction of
the magnetic field at that position. An X means the direction of the magnetic
field is into the page and an O means the direction of the magnetic field is out
of the page. The green arrow indicates the magnetic force on the charge and the
black arrow indicates the velocity of the charge.
What happens to the magnetic
force on the charge when the velocity increases?
Stays the same
What happens to the magnetic force on the charge when the magnetic field
strength increases in magnitude?
What happens to the magnetic force on the charge when the mass of the charge
Why does the trajectory of the charge change so much when the mass of the charge
Because the force stays the same. When the force stays the same but the mass increases, by Newton's 2nd law, the acceleration must decrease causing the charge to loop around in larger circles.
Under what condition can a charge move through a magnetic field and not experience a
If the charge's motion is parallel to the direction of the magnetic field there will be no magnetic force (sin 90 degrees = 0)
Why does the charge suddenly change its path when crossing the boundary from a
magnetic field going into the page to a magnetic field going out of the page?
By the right hand rule, when the magnetic field is pointed in an opposite direction, the magnetic force will also be in the opposite direction.
Is the charge in the applet a positive or negative charge?
What would change about the trajectory of an identical but opposite charge?
The force would be opposite, so it's path would trace out a loop going in the opposite direction.
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Was there anything that you didn't understand in the reading assignment?
What was confusing to you?