Quiz 14 - physics
Which of the following cannot induce a voltage in a loop of wire?
Expanding or contracting the loop in a region where there is no magnetic field.
Imagine that this classroom contains a constant magnetic field that points from the front to the back. In front of you a negative charge is slowly moving horizontally to your left. As you watch, the magnetic force on the charge
deflects the charge into a counterclockwise vertical circle.
When a switch is closed allowing current to flow in coil A, the current induced in a nearby coaxial but unconnected coil B
will flow only momentarily and then stop.
The south pole of a bar magnet is moved toward a short helical coil of wire (solenoid) along the axis of the coil. The coil has 100 turns and the ends of the coil are connected to form a closed circuit. If the coil is replaced with a single loop of the same type of wire, and the magnet is moved exactly as before, the current induced in the loop is Group of answer choices
100 times smaller
Bar A has one end painted green and the other end red and may or may not be a magnet. A student brings the north pole of a bar magnet M close to the green end of A. He observes that the green end is attracted. He can conclude that Group of answer choices
A might be a magnet; this observation does not provide enough information to determine whether or not it is.
Which of these will always produce a magnetic field?
A moving charge
A little magnetic compass has a needle whose tips are clearly labeled N and S. The compass is placed next to a single circular loop of wire lying flat on a wooden table. The current in the loop is clockwise. What happens
None of these.
The scientist credited with discovering that electric currents produce magnetic fields was
Oersted.
A battery is causing a large current in a solenoid (helical coil of wire). A bar magnet is held at rest nearby, aligned with the axis of the solenoid, with its south pole closest to the solenoid. The bar magnet is being repelled by the solenoid. Which of the following statements is true of the conventional current in the solenoid?
The current in the solenoid is flowing clockwise as seen from the bar magnet.
The sketch below shows a bar magnet in a loop of wire with the bar perpendicular to the plane of the loop. The left-hand side shows the magnet being spun around its long axis while on the right side the magnet is turned end-over-end. Which case creates a larger induced current in the loop?
The right-hand side.
What would happen if you had a car made completely of plastic, with no metal parts, and you drove over a vehicle sensor embedded in the road surface?
The sensor would not notice you or your vehicle, and you'd be stuck at the red light.
A positive charge is released from rest near a bar magnet. The magnetic force on the charge
There is no magnetic force on the charge.
A loop of wire is oriented in the magnetic field as shown below (the plane of the loop is perpendicular to the direction of the magnetic field). Which of the following is true?
There will be an induced current if the loop is moved either up or down.
In outer space, you observe a straight stream of electrons flowing past you at 14.5 miles per second, about the same speed that Mars moves on its orbit around the sun.
You observe no magnetic field.
A current flowing through a long, straight wire causes a magnetic field that points
along concentric circles around the wire.
The magnetic pole near the Earth's north geographic pole actually has to be
an S pole, because it attracts the N pole of your compass needle.
Two identical coils of wire are placed on a single horizontal wooden broom handle. The coils are separated by a few centimeters. We now run identical currents in the same direction through each coil. The coils experience
an attractive magnetic force.
The south pole of a bar magnet is moved toward an aluminum ring, along the axis of the ring. As the magnet approaches, the changing magnetic flux induces an electric current in the ring that, when seen from the bar magnet, corresponds to positive charge carriers flowing Group of answer choices
clockwise.
A horizontal straight wire carries a current from east to west. The resulting magnetic field lines are
closed circles perpendicular to the wire directed clockwise as viewed from the east.
A permanent magnet is produced when
magnetic fields of large groups of individual atoms are permanently aligned.
Magnetic fields affect
only electric charges in motion.
The south pole of a bar magnet is moved toward a short helical coil of wire (solenoid) along the axis of the coil. The coil has 100 turns and the ends of the coil are connected to form a closed circuit. If the coil is replaced with a single loop of the same type of wire, and the magnet is moved exactly as before, the magnet experiences a force that is
repulsive and 100 times smaller.
You could use two parallel wires to move objects 1 and 2 apart if each wire is embedded in its own object and if
the currents in the wires are in opposite directions.
Two particles move into a magnetic field. They enter moving at the same speed and direction. The magnitude of the charge on each is known to be the same. One particle curls to the right and the other to the left upon entering the field, the one on the left moving in a larger circle than the one on the right. From this we can say that
the leftward moving particle has more mass and its charge is opposite the other particle.
A magnetic compass points towards the north geographic pole of the Earth because
there is a south magnetic pole near the north geographic pole.
In outer space, you observe a straight stream of electrons flowing past you at 14.5 miles per second, about the same speed that Mars moves on its orbit around the sun.
up
Electrons flow around a circular wire loop in a horizontal plane, in a direction that is clockwise when viewed from above. This causes a magnetic field. Inside the loop, the direction of this field is
up, toward the viewer.
A long straight wire carries a current. A positive charge moves toward the wire in a direction perpendicular to the wire. The direction of the force on the charge will be
parallel to the wire opposite the direction of the current.
You see a positively charged helium ion in space, and it is at rest with respect to your spacecraft. Since you are studying for the final exam, you decide to experiment. You slowly push the N pole of a bar magnet closer to the helium ion. What happens to the helium ion?
Nothing happens, because the ion is not moving.
A bar magnet and an electrically polarized object are placed next to each other on a table. What happens?
Nothing happens.
A horizontally moving positive sodium ion enters a magnetic field that points up. The magnetic force pushes the charge out of its original path.
Out of the page
A bar magnet is broken in half and the magnetic field around one piece is mapped out. What is wrong with this picture?
There is no south pole.
A positively charged ping pong ball is sitting stationary on the floor in the center of a room. There is also a constant, uniform magnetic field in the room that points toward the ceiling. If I now start the ball rolling toward the back of the room, the resultant motion of the ball, as observed from the ceiling, will be Group of answer choices
a horizontal, clockwise circle.
Think of a closed rectangular loop of wire around the edge of this page. A magnetic field perpendicular to the page points upward and increases in strength in a certain time. During this time the conventional current induced in the loop will be Group of answer choices
clockwise
Imagine a magnetic field pointing into the plane of this page. An electron moves across the paper from left to right. The direction of the magnetic force on the electron will be
in the plane of the paper and toward the bottom of the page.
If an electron moves in a magnetic field,
it only feels a force if its velocity vector is not parallel (or antiparallel) to the direction of the magnetic field.
In the southern hemisphere, the north pole of a compass needle
points away from the south geographic pole because there is a north magnetic pole there.
An ideal transformer is used to either increase or decrease the voltage in an AC circuit. When the output voltage is greater than the input voltage of a transformer then Group of answer choices
the power output is the same as the power input.
If an electron is placed at rest near a bar magnet, the electron will
not move at all.
When a current is induced by a changing magnetic field B1, the current always produces a second magnetic field B2 such that
It is not possible to tell whether the combined field is stronger or weaker than B1 without knowing how B1 is changing.
