Magnetism
A current-carrying wire 0.50 m long is positioned perpendicular to a uniform magnetic field. If the current is 10.0 A and there is a resultant force of 3.0 N on the wire due to the interaction of the current and field, what is the magnetic field strength?
0.60 T
A wire 48 m long carries a current of 18 A from west to east. If a magnetic field of 8.3 x 10-⁴ T directed toward the south is acting on the wire, find the direction and magnitude of the magnetic force. (Remember F = BIL)
0.72 N downward.
An electron that moves with a speed of 3.0 x 10⁴ m/s perpendicular to a uniform magnetic field of 0.40 T experiences a force of what magnitude? (q⬇️(e) = 1.60 x 10-¹⁹ C)
1.9 x 10-¹⁵ N
An electron moves north at a velocity of 6.2 x 10⁶ m/s and has a magnetic force of 2.1 x 10-¹⁸ N exerted on it. If the magnetic field points upward, what is the magnitude of the magnetic field? (Remember F = qvB)
2.1 x 10-⁶ T
An electron moves across Earth's equator at a speed of 2.5 x 10⁶ m/s and in a direction 35 degrees north of east. At this point, Earth's magnetic field has a direction due north, is parallel to the surface, and has a value of 0.10 x 10-⁴ T. What is the magnitude of the force acting on the electron due to its interaction with Earth's magnetic field? (q⬇️(e) = 1.60 x 10-¹⁹ C)
3.3 x 10-¹⁸ N (wrong)
One useful way to model magnetic field strength is to define a quantity called magnetic flux. Which of the following definitions for magnetic flux is correct?
All of the above. (The number of field lines that cross a certain area, AB cos 0, [surface area] X [magnetic field component normal to the plane of surface])
Under which of the following conditions is the net magnetic force on a charged particle equal to zero?
All of the above. (When the particle is stationary, when the particle is moving parallel to the magnetic field, and when the particle is not charged.)
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.
There are four coils of wire being used as electromagnets. They all have the same size and are made up of the same material, but have a different number of loops. Which coil will produce a magnetic field with the maximum strength when the same amount of current passes through all coils? (One has 10 loops, one has 25 loops, one has 30 loops, and one has 45 loops.)
A coil having 45 loops.
Which of the following provides the best example of a solenoid?
A coil of wire wrapped around a nail, with each end of the wire connected to the positive and negative terminals of a battery.
Dropping or heating a magnet will not weaken it because the domains will stay in alignment.
False.
A current in a long, straight wire produces a magnetic field. These magnetic field lines
Form circles that go around the wire.
The lines of the magnetic field around a current-carrying wire
Form concentric circles around the wire.
How can you increase the strength of a magnetic field inside a solenoid?
Increase the number of coils per unit length. (Wrong)
In soft magnetic materials such as iron, what happens when an external magnetic field is removed?
The orientation of domaines fluctuates. (Wrong)
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.
A stationary positive charge, Q, is located in a magnetic field, B, which is directed toward the right. What is the direction of the magnetic force on Q?
There is no magnetic force.
A magnetic domain is a group of atoms whose magnetic fields are aligned in a common direction.
True.
A wire in a lamp that is turned on would have a magnetic field around it.
True.
In a magnet, the magnetic field points from the south pole to the north pole.
True.
[N S] [S N] The magnets shown in the figure above will repel each other.
True.
[S N] [S N] The magnets in the figure will attract each other.
True.
Which of the following citations is not true for magnets?
Unlike poles repel each other.
What is true about an electric motor?
Both A and B A. Every half-turn of a current carrying wire the current is reduced causing it to spin. B. The current carrying loop is able to turn because the magnetic force is always at a right angle to it.
In a magnetized substance, the domains
Line up mainly in one direction.
All of the following statements about magnetic field lines around a permanent magnet are true except which one?
Magnetic field lines appear to end at the north pole of a magnet.
A conductor carrying a current is arranged so that electrons flow in one segment from east to west. In what direction is the magnetic field moving? (Hint: recall that current is defined as the motion of positive charges.)
North (wrong)
The direction of the force on a current-carrying wire in an external magnetic field is
Parallel to the current and to the magnetic field. (Wrong)
Which statement describes Earth's magnetic declination?
The angle between true north and north indicated by a compass.
Where is the magnitude of the magnetic field around a permanent magnet greatest?
The magnitude is greatest close to the poles.
