Ch 21 Magnets
At points near the Earth's equator, one would expect the magnetic inclination angle to be approximately
0 degrees
Where is the magnitude of the magnetic field around a permanent magnet greatest?
Close to the poles
A current in a solenoid coil creates a magnetic field inside the coil. The field strength is directly proportional to the
Current
In a magnetized substance, the domains
line up mainly in one direction
A solenoid is in an upright position. A clockwise current of electrons causes the solenoid to have a ________ magnetic pole at its bottom end. If a compass is placed at the top of the solenoid, the north pole of the compass would be
north; attracted
A current-carrying conductor in and perpendicular to a magnetic field experiences a force that is
perpendicular to the current
The direction of the force on a current-carrying wire in an external magnetic field is
perpendicular to the current and to the magnetic field
Which orientation characterizes the magnetic domains in a nonmagnetized piece of iron?
random
The magnetic field of a bar magnet is shown in the figure above. Is the magnet's north pole at A or B?
A
Which compass needle orientation in the figure above might correctly describe the magnet's field at that point?
A
How can the magnetic field around a permanent magnet be determined?
A compass
A current in a long, straight wire produces a magnetic field. These magnetic field lines
Form circles that go around the wire
Describe how the right-hand rule applies to the magnetic field produced by the current in a straight conductor.
If the wire is grasped in the right hand with the thumb in the direction of the current, the fingers will curl in the direction of the magnetic field.
In soft magnetic materials such as iron, what happens when an external magnetic field is removed?
The orientation of domains changes, and the material returns to an unmagnetized state
Electrons move from the south to the north in a wire. What is the direction of the magnetic field at a point directly above the wire?
West
What is the path of an electron moving perpendicular to a uniform magnetic field?
a circle
Which magnetic pole is at the geographic South Pole of Earth?
Magnetic north
Which magnetic pole is at the geographic North Pole of Earth?
Magnetic south
If the head of an iron nail touches a magnet, the nail will become a magnet by induction. If the nail touches the north pole of the magnet, what kind of pole is at the point of the nail? Explain.
North, because the head of the nail is attracted to the north, therefore making it south. That makes the other side of the nail (the point) north
A current in a solenoid with N turns creates a magnetic field inside the solenoid. The magnetic field strength is directly proportional to the
Number of turns in the loop and the strength of the current
If a wire is carrying a strong, steady current, the magnetic field is
Proportional to the current and inversely proportional to the distance from the wire
A bar magnet is suspended and allowed to rotate freely. If the magnetic field of Earth is considered to be equivalent to that of a large bar magnet, which pole of the suspended magnet would point toward the magnetic north pole of Earth?
South pole of the magnet
Which describes magnetic declination?
The angle between directions to true north and magnetic
The current in a long wire creates a magnetic field in the region around the wire. How is the strength of that field at a given distance, r, from the wire's center related to r?
The field is inversely proportional to r
When an iron rod is inserted into a solenoid coil's center, the magnetic field produced by the current in the loops
causes alignment of the domains in the iron
In a permanent magnet,
domain alignment persists after the external magnetic field is removed
A microscopic magnetic region composed of a group of atoms whose magnetic fields are aligned in a common direction is called a ______. In most materials, when these groups are randomly distributed, the substance will show ______ magnetism.
domain; no
If a proton is released at the equator and falls toward Earth under the influence of gravity, the magnetic force on the proton will be toward the
east
A solenoid is in an upright position on a table. A counterclockwise current of electrons causes the solenoid to have a ______ magnetic pole at its bottom end. If a compass is placed at the top of the solenoid, the north pole of the compass would be
south; repelled
What is the path of an electron moving parallel to a uniform magnetic field?
straight line
Consider two long, straight, parallel wires, each carrying a current I. If the currents move in the same direction,
the two wires will attract each other
Consider two long, straight, parallel wires, each carrying a current I. If the currents move in opposite directions,
the two wires will repel each other
