Magnetism
21 questions tagged Magnetism — spanning every one of the seven Ws.
Why can a magnet levitate over a superconductor?
A superconductor expels magnetic fields, so it can lock a magnet in place through a phenomenon called flux pinning. This creates stable levitation at very low temperatures.
Why do magnets have north and south poles instead of a single pole?
Magnets are dipoles because their magnetic fields are created by aligned moving charges and atomic electron spins. If you cut a magnet in half, you get two smaller magnets, each with both poles.
Where is the world's strongest magnetic field created in the lab?
The strongest steady magnetic fields are created at the National High Magnetic Field Laboratory, best known for its site in Tallahassee, Florida. It is one of the leading places for ultra-strong magnet research.
Which element has the strongest permanent magnetism in a pure form?
Iron is the best-known pure element for ferromagnetism at room temperature, though alloys like neodymium-iron-boron are stronger magnets overall. Pure iron is the classic elemental magnet.
How do magnets repel and attract each other?
Magnets create magnetic fields that push or pull depending on their pole orientation and the alignment of nearby magnetic moments. Opposite poles attract, and like poles repel.
How does a metal detector work?
A metal detector sends out a changing magnetic field; when that field passes through metal, it creates tiny electric currents in the object, which the detector senses.
Why do magnets attract some metals but not others?
Magnets attract metals such as iron, nickel, and cobalt because their electrons can align into magnetic domains. In most other metals, those tiny magnetic effects cancel out, so there is little or no visible attraction.
Why do compasses point north?
A compass needle points north because it is a tiny magnet that aligns with Earth’s magnetic field. The “north” end of the needle is attracted toward the magnetic south near Earth’s geographic North Pole.
Why does a permanent magnet lose its strength when heated?
Heating makes the atoms in a magnet vibrate more, which disrupts the alignment of its magnetic domains. If it is heated enough, it can reach the Curie temperature and lose ferromagnetism.
Why do refrigerator magnets stick to steel but not to aluminum?
Steel contains iron, which is ferromagnetic and strongly attracted to magnets. Aluminum is not ferromagnetic, so ordinary magnets do not stick to it in the same way.
Why do charged particles bend in a magnetic field?
Charged particles bend because a magnetic field exerts a force at right angles to their motion. That sideways force changes the direction of travel without necessarily changing the speed.
Where is the first successful demonstration of nuclear magnetic resonance generally credited?
It is credited to laboratories at Harvard University and Stanford University in 1946. Felix Bloch worked at Stanford, and Edward Purcell worked at Harvard.
Which force makes magnetism possible?
The electromagnetic force makes magnetism possible. Magnetism is one aspect of electromagnetism, linked to moving electric charges.
Whose idea explained why magnets have north and south poles at the microscopic level?
Pierre Curie studied symmetry and magnetism, helping lay the groundwork for understanding magnetic domains and fundamental asymmetries. His work was influential in modern physics.
How does a planet get a magnetic field?
A magnetic field is usually generated by moving liquid metal inside a planet, creating a dynamo as the planet rotates.
How do magnets work if there is no magnetic charge like electric charge?
Magnetism comes from moving electric charges and quantum spin, not from separate magnetic charges in ordinary materials. Magnetic north and south always appear together as dipoles.
What is the Meissner effect?
The Meissner effect is the expulsion of magnetic fields from a superconductor when it becomes superconducting. It is one of the clearest signs of superconductivity.
Where is the world’s strongest known magnetic field found on Earth?
The strongest sustained magnetic fields created on Earth are produced in laboratory facilities, especially at the National High Magnetic Field Laboratory in the United States. One of its major sites is in Tallahassee, Florida.
Which force explains why magnets attract or repel each other?
The electromagnetic force explains magnetism. Magnetic fields arise from moving electric charges and the quantum properties of electrons.
How does Jupiter produce such strong auroras?
Jupiter's huge magnetic field and fast rotation accelerate charged particles into its upper atmosphere, creating powerful auroras.
How does magnetic force make a compass needle point north?
Earth acts like a giant magnet, and a compass needle aligns with its magnetic field. The needle points toward magnetic north, not exactly geographic north.