Chapter 32 Magnetism Magnetic force Magnetic force on a moving charge The Hall Effect
Magnetism
In 8th century, Greeks had discovered that a piece of mineral magnetite (known as loadstone, an oxide of iron) can attract a piece of iron.
Later, it was discovered that one piece of magnetite can either attract or repel another piece, depending on their relative orientation.
By the 12th century, an experiment was performed in which a small needle-type magnetite was suspended. The piece spontaneously rotated and eventually came to rest with one end pointing roughly towards the earth’s north geographic pole. That end was painted then as red. The opposite was then towards south pole. Like poles repel, and unlike poles attract.
This rule is very similar to the rule for the interaction of electric charges.
Magnetism and moving charges
Does there exist in nature a “magnetic test charge” that could be used to determine the strength and directions of the magnetic field, just as we used the force on an electric test to determine the electric field? Answer:
No
Can we use an electric test charge to probe a magnetic field?
Answer: Yes, but only charge is moving relative to the source of the magnetic field. A magnetic field exerts no force on an electric charge at rest.
If the electric charges in motion can be used to probe magnetic field, can electric charges in motion also produce magnetic fields?
Answer: Yes
In electrostatics, we associated an electrical potential energy with a test charge in an electric field. Is there a “magnetic potential energy” associated with a moving electric test charge in a magnetic field?
Answer: NO
The magnetic force on a moving charge
The magnetic force on a moving charge
The magnetic force on a moving charge
The magnetic force on a moving charge
The Hall Effect
The Hall Effect
The Hall Effect
The Hall Effect