Physics Exam 2 part 2
An electron moving along the +x axis enters a region where there is a uniform magnetic field in the +y direction. What is the direction of the magnetic force on the electron? (+x to right, +y up, and +z out of the page.)
-z direction
two long parallel lines carry 20A and 5.0A long answer
0.16 from the 20A wire
a proton with speed 3.0x10^6 magnetic field?
0.16T
strength of magnetic field 5cm and 4A
1.6x10^-5T
At double the distance from a long current-carrying wire, the strength of the magnetic field produced by that wire decreases to
1/2 of its original value
what distance from a ling straight wire of current 5.0A
2.0cm
high power line 1000A
2.0x10^-5
Four long parallel wires
2.1x10^-5T
two long parallel wires of 5 and 8
2.7x10^-5N repulsive
what is the magnetic field at the center of a circular loop of wire radius 4cm
3.1x10^-5T
a very long straight wire carries 25A
3.3x10^-5T
Consider two current-carrying circular loops. Both are made from one strand of wire and both carry the same current, but one has twice the radius of the other. Compared to the magnetic moment of the smaller loop, the magnetic moment of the larger loop is
4 times stronger
Two long parallel wires carry equal currents. The magnitude of the force between the wires is F. The current in each wire is now doubled. What is the magnitude of the new force between the two wires?
4F
two long parallel lines carry currents of 20A and 5.0A short answer
5.0x10^-5T
how much flow for 1.0x10^-3 1cm from wire
50A
two parallel lines carry currents of 10A in opposite directions
6.7x10^-6
The maximum torque on a current carrying loop occurs when the angle between the loop's magnetic moment and the magnetic field vector is
90 degrees
1 T is equivalent to
M/A*m
What fundamental fact underlies the operation of essentially all electric motors?
a current- carrying conductor placed perpendicular to a magnetic field will experience a force
An electric current produces
a magnetic field
If the south pole of one bar magnet is brought near the north pole of a second bar magnet, the two magnets will
attract
A charged particle moves across a constant magnetic field. The magnetic force on this particle
causes the particle to accelerate
A horizontal wire carries a current straight toward you. From your point of view, the magnetic field caused by this current
circles the wire on the counter- clockwise direction
At a particular instant, an electron moves eastward at speed V in a uniform magnetic field that is directed straight downward. The magnetic force that acts on it is
directed to the south
A velocity selector consists of a charged particle passing through crossed electric and magnetic fields. The forces exerted by these fields are in opposite directions, and only particles of a certain velocity will move in a straight line. In the following, disregard the magnitudes of the fields. In a velocity selector, the particles move toward the east, and the magnetic field is directed to the north. What direction should the electric field point?
down
A charged particle moves and experiences no magnetic force. From this we can conclude that
either no magnetic field exists or the particle is moving parallel to the field
A charged particle is injected into a uniform magnetic field such that its velocity vector is perpendicular to the magnetic field vector. Ignoring the particle's weight, the particle will
follow a circular path
A charged particle moves with a constant speed through a region where a uniform magnetic field is present. If the magnetic field points straight upward, the magnetic force acting on this particle will be maximum when the particle moves
in a plane parallel to the earth's surface
When placed askew in a magnetic field, a current carrying loop that is free to rotate in any direction will experience a torque until its magnetic moment vector
is aligned with the magnetic field
Two long parallel wires placed side-by-side on a horizontal table carry identical current straight toward you. From your point of view, the magnetic field at the point exactly between
is zero
when a current carrying wire is in your right hand, thumb in the direction of the current, your fingers point in the direction of the
magnetic field lines
Consider two current-carrying circular loops. Both are made from one strand of wire and both carry the same current, but one has twice the radius of the other. Compared to the magnetic field at the center of the smaller loop, the magnetic field at the center of the larger loop is
none of the given answers
A long straight wire carries current toward the east. A proton moves toward the east alongside and just south of the wire. What is the direction of the force on the proton?
north
A particle carrying a charge of +e travels in a circular path in a uniform magnetic field. If instead the particle carried a charge of +2e, the radius of the circular path would have been
one-half the original radius
The direction of the force on a current-carrying wire in a magnetic field is described by which of the following?
perpendicular to the current only
Two long parallel wires placed side-by-side on a horizontal table carry identical size currents in opposite directions. The wire on your right carries current toward you, and the wire on your left carries current away from you. From your point of view, the magnetic field at the point exactly midway between the two wires
points down
current carrying loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, outside the loop? The magnetic field
points straight down
A current carrying circular loop of wire lies flat on a table top. When viewed from above, the current moves around the loop in a counterclockwise sense. What is the direction of the magnetic field caused by this current, inside the loop? The magnetic field
points straight up
The magnetic field produced by a long straight current-carrying wire is
proportional to the current in the wire and inversely proportional to the distance from the wire
If the north poles of two bar magnets are brought close to each other, the magnets will
repel
A vertical wire carries a current straight down. To the east of this wire, the magnetic field points
south
The Earth's geographic North Pole is magnetically a
south pole
The south pole of a magnet points toward the Earth's
south pole
The SI unit of magnetic field is the
tesla
The force on a current-carrying wire in a magnetic field is equal to zero when
the current is parallel to the field lines
The force on a current-carrying wire in a magnetic field is the strongest when
the current is perpendicular to the field lines
A circular wire loop lies in a horizontal plane on a table and carries current in a counterclockwise direction when viewed from above. At this point, the Earth's magnetic field points to the north and dips below the horizontal. Which side of the coil tends to lift off of the table because of the torque caused by the currents interaction with the magnetic field?
the south side
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in the same direction,
the wires attract each other
Two long parallel wires are placed side-by-side on a horizontal table. If the wires carry current in opposite directions,
the wires repel each other
An electron has an initial velocity to the south but is observed to curve upward as the result of a magnetic field. The direction of the magnetic field is
to the west
A wire lying in the plane of the page carries a current toward the bottom of the page. What is the direction of the magnetic force it produces on an electron that is moving perpendicularly toward the wire, also in the plane of the page, from your right?
toward the bottom of the page
A charged particle is observed traveling in a circular path in a uniform magnetic field. If the particle had been traveling twice as fast, the radius of the circular path would be
twice the original radius
If a bar magnet is divided into two equal pieces,
two magnets result
A vertical wire carries a current straight up in a region where the magnetic field vector points due north. What is the direction of the resulting force on this current?
west