All AP Physics 2 Resources
Example Questions
Example Question #1 : Magnetism And Electromagnetism
There is a particle with a charge of moving
perpendicular through a magnetic field with a strength of
. What is the force on the particle?
The equation for force on a moving charged particle in a magnetic field is
.
Because the charge is moving perpendicularly through the magnetic field, we don't have to worry about the cross product, and the equation becomes simple multiplication.
Therefore, the force experienced by the particle is 3619N.
Example Question #1 : Electromotive Force And Magnetic Flux
A conductive rod is moving through a region of magnetic field, directed out of the page as diagrammed above. As a result of its motion, the mobile charge in the rod separates, creating an electric potential across the length of the rod. The length of the rod is 0.12m and the magnitude of the magnetic field is 0.022T. If the rod is moving with velocity , what is the magnitude and direction of the potential from one end of the rod to the other?
the top is at a higher potential than the bottom
the top is at a higher potential than the bottom
the top is at a lower potential than the bottom
the top is at a lower potential than the bottom
the top is at a higher potential than the bottom
the top is at a higher potential than the bottom
For a conductor moving in a magnetic field, cutting straight across the field lines, a potential is generated where
is the potential or EMF,
is the magnetic field strength, and
is the conductor's velocity relative to the field.
As the rod moves, the positive charge feels an upward-directed force by the right-hand rule, and the negative a downward force resulting in the top being at a higher potential than the bottom of the rod.
Example Question #1 : Electromotive Force And Magnetic Flux
A conductive rod is moving through a region of magnetic field, as diagrammed above. As a result of its motion, mobile charge carriers in the conductor separate, creating an electric potential across the rod. When, if ever, do the charge carriers cease this motion?
The motion stops when the electric potential equals the magnetic field strength.
The motion stops when the magnetic field created by the separated charges equals the external magnetic field.
The motion stops when the electric field created by the separated charges creates an equal and opposite force to the magnetic force created by the rod's motion.
The motion does not stop. Mobile charge carriers continue to separate as long as the rod remains in motion.
The motion stops when the electric field strength created by the separated charge equals the magnetic field strength.
The motion stops when the electric field created by the separated charges creates an equal and opposite force to the magnetic force created by the rod's motion.
The separated charge creates a potential . This potential results in an electric field
When this induced electric field creates a force
equal to the magnetic force
on the mobile charge carriers, motion stops. Of course, if an electric circuit is created drawing current from the rod, motion will resume to rebuild the field.
Example Question #1 : Electricity And Magnetism
Suppose that a proton moves perpendicularly through a magnetic field at a speed of . If this proton experiences a magnetic force of
, what is the strength of the magnetic field?
.
To solve this question, we need to relate the speed and charge of the particle with the magnetic force it experiences in order to solve for the magnetic field strength. Thus, we'll need to use the following equation:
Also, we are told that the particle is moving perpendicularly to the magnetic field.
Rearrange to solve for the magnetic field, then plug in known values and solve.
Example Question #1 : Magnetic Fields
Suppose that a positively charged particle with charge moves in a circular path of radius
in a constant magnetic field of strength
. If the magnetic field strength is doubled to
, what effect does this have on the radius of the circular path that this charge takes?
To answer this question, we need to realize that the particle is moving in a circular path because of some sort of centripetal force. Since the charge is moving while within a constant magnetic field, we can conclude that it is the magnetic force that is responsible for the centripetal force that keeps this charge moving in a circle. Thus, we need to relate the centripetal force to the magnetic force.
The above equation shows us that the radius of the circular path is directy proportional to the mass and velocity of the particle, and inversely proportional to the charge of the particle and the magnetic field strength. Thus, if the value of the magnetic field is doubled, the above equation predicts that the value of the radius would be cut in half.
Example Question #1 : Magnetic Fields
loops of current carrying wire form a solenoid of length
that carries
and have radius
. Determine the magnetic field at the center of the solenoid.
Using:
Where:
is the magnetic field
is the number of coils
is the current in the solenoid
is the length of the solenoid
is
Plugging in values:
Example Question #1 : Electricity And Magnetism
There is a loop with a radius of and a current of
. Determine the magnitude of the magnetic field at the center of the loop.
None of these
Using the Biot-Savart law:
Where is the radius of the loop
is the current
is the distance from the center of the loop
Plugging in values:
Example Question #1 : Magnetic Fields
A circular circuit is powered by a battery. How will the magnetic field change if the battery is removed and placed in the opposite direction?
The magnetic field will have the same magnitude and direction
The magnetic field will have the same magnitude, albeit in the opposite direction
The magnetic field will become zero
None of these
The magnetic field will double in magnitude and flip directions
The magnetic field will have the same magnitude, albeit in the opposite direction
Reversing the battery will reverse the direction of the current. Using the right hand rule, it can be seen that this will also reverse the direction of the magnetic field. Since the magnitude of the current stays the same, the magnitude of the magnetic field will as well.
Example Question #1 : Magnetic Fields
A circular circuit is powered by a battery. How will the magnetic field change if a second
battery is added in the same direction as the first?
The magnetic field will double in magnitude and have the same direction.
The magnetic field will stay the same
None of these
The magnetic field will quadruple
The magnetic field will become zero
The magnetic field will double in magnitude and have the same direction.
Based on the Biot-Savart law:
Doubling the voltage will double the current, which will double the magnetic field. The direction will stay the same.
Example Question #1 : Magnetism And Electromagnetism
If the north end of a magnetic points towards the geographic north pole, that means that the geographic north pole is a magnetic __________ pole.
Electrical
North
Mono
None of these
South
South
Magnets will align themselves with the surrounding magnetic field. Thus, if the north pole of a magnet is pointing north, the direction of the magnetic field must be pointing north. Magnetic fields point towards magnetic south poles, so the geographic north pole is actually a magnetic south pole.
All AP Physics 2 Resources
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