Magnet

A magnet has a hidden force.

This force pulls on iron and steel. It can also push other magnets away.

Some magnets stay magnetic all the time. You might use one to hold notes on a fridge.

These are called permanent magnets.

Other magnets use electricity to work. When electricity flows through a wire, it becomes a magnet. This is called an electromagnet.

Long ago, people found natural magnets in rocks. These rocks are called lodestones. People used them to make early compasses.

Magnets are very useful tools. They help us in many ways every day.

A magnet has a hidden force called a magnetic field.

This field is invisible. It can pull on certain metals. These metals are called ferromagnetic materials. Iron, nickel, and cobalt are examples.

Some magnets are permanent. They keep their power all the time. You might see these on a fridge.

Other magnets use electricity. These are called electromagnets. They work when electricity flows through a wire coil. The magnet stops working when the power goes out.

Long ago, people found natural magnets in rocks. These rocks are called lodestones. They are pieces of iron ore. People used lodestones to make the first compasses.

Magnets have two ends. We call these the north and south poles. Opposite poles pull toward each other. This is called attraction. Like poles will push each other away. This is called repulsion. If you break a magnet in half, you do not get separate poles. You just get two smaller magnets. Each one will still have a north and south pole.

A magnet is a special object that creates a magnetic field.

This field is invisible, but it has a very strong force. It can pull on certain metals, which are called ferromagnetic materials. Common examples of these metals include iron, nickel, and cobalt.

Some magnets are permanent, meaning they keep their magnetic power all the time. You might see these small magnets holding notes on a refrigerator door. Other types of magnetism are much weaker and need special tools to see.

Magnets work in a few different ways depending on how they are made. A permanent magnet stays magnetized because of its internal structure. Scientists make these using "hard" materials like alnico or ferrite. These materials go through special processing in a strong magnetic field. This helps align their tiny internal parts so they stay magnetic.

Another way to make a magnet is to use electricity. This is called an electromagnet, which uses a coil of wire. When an electric current flows through the wire, it becomes a magnet. When the electricity stops, the magnetic force disappears.

People have been studying magnets for thousands of years. Ancient people discovered natural magnets called lodestones, which are pieces of iron ore.

The word magnet comes from the Greek word for "stone from Magnesia." Some people think this refers to a place in Greece or Anatolia. Early descriptions of magnets appear in records from India and China. Around 2,500 years ago, people began writing about how these stones worked.

Many important discoveries helped us understand magnetism better over time. In 11th-century China, people found that cooling hot iron could make it a magnet. This discovery helped them create the first navigational compasses.

Later, in 1743, Daniel Bernoulli invented the horseshoe magnet. This shape helps the magnet stay strong by returning magnetic lines to the opposite pole. In 1820, Hans Christian Ørsted found that electricity could move a compass needle. This led William Sturgeon to create the first iron-cored electromagnet in 1824.

Every magnet has two ends called poles. We call them the north pole and the south pole. The north pole is the end that points toward the Earth's North Magnetic Pole. If you put two magnets together, opposite poles will pull toward each other. This is called attraction, while similar poles will push away. If you break a magnet in half, you do not get a separate north and south piece. Instead, you simply get two new, smaller magnets. Each new piece will still have its own north and south poles.

A magnet is a material or object that produces a magnetic field. This field is invisible, yet it is responsible for the magnet's most notable property. It exerts a force that pulls on ferromagnetic materials, such as iron, steel, nickel, and cobalt. It can also attract or repel other magnets.

While most substances respond weakly to magnetic fields through other types of magnetism, ferromagnetic and ferrimagnetic materials are the only ones strongly attracted to a magnet. These materials are essential for creating the permanent magnets we use in everyday life, like the ones on a refrigerator door.

Scientists categorize ferromagnetic materials into two distinct types: "soft" and "hard." Magnetically soft materials, such as annealed iron, can be magnetized easily. However, they do not tend to stay magnetized for long. In contrast, magnetically hard materials stay magnetized. Permanent magnets are manufactured from these hard materials, such as alnico or ferrite. During manufacturing, these materials undergo special processing in a strong magnetic field. This process aligns their internal microcrystalline structure, making them very difficult to demagnetize.

To understand how a magnet behaves, we can look at two different scientific models. The magnetic pole model is a convenient way to think about magnets. In this view, a magnet has a north pole and a south pole. If you break a bar magnet in half to try and separate these poles, you will not succeed. Instead, you will simply create two smaller magnets, each with its own north and south pole.

Another model is the Ampère model. This model suggests that magnetization comes from microscopic, or atomic, circular currents throughout the material. These are called Ampèrian currents. For a cylindrical bar magnet, these tiny currents make the magnet behave as if a large sheet of electric current is flowing around its surface.

Humanity's relationship with magnetism began with lodestones. These are naturally occurring pieces of magnetite, which is a type of iron ore.

The word "magnet" comes from the Latin *magnetum*, meaning lodestone. This word likely traces back to the Greek term for "stone from Magnesia." While the exact location of Magnesia is debated, it may refer to a region in Greece or Anatolia. Ancient people used suspended lodestones as the very first magnetic compasses. The earliest written descriptions of these properties come from Anatolia, India, and China from approximately 2,500 years ago.

Significant historical developments changed how we use magnetic force. In 11th-century China, researchers discovered that quenching red-hot iron aligned with Earth's magnetic field would leave it permanently magnetized. This led to the navigational compass described in the *Dream Pool Essays* of 1088. Later, in 1743, Daniel Bernoulli invented the horseshoe magnet. This shape prevents a magnet from demagnetizing itself by returning the magnetic field lines to the opposite pole.

In 1820, Hans Christian Ørsted discovered that electric currents could deflect a compass needle. This discovery allowed William Sturgeon to develop an iron-cored electromagnet in 1824. Finally, Joseph Henry advanced the electromagnet into a commercial product by 1830, providing access to strong magnetic fields for the first time.

Magnetism can be measured using several specific values. The overall strength of a magnet is called its magnetic moment. This is a vector that characterizes the magnet's total properties. For a bar magnet, the direction of the magnetic moment points from the south pole to the north pole. The strength of the magnetic field itself, often called the B field, is measured in teslas.

We can also measure magnetization, which is the local value of the magnetic moment per unit volume. For example, a good bar magnet might have a magnetic moment of 0.1 A·m2. Iron can reach a magnetization of around one million amperes per meter, which explains why iron magnets are so effective.

Today, magnetism is integrated into many complex technologies. Electromagnets are a primary example. These are made from a coil of wire that acts as a magnet only when an electric current passes through it. If the current stops, the magnetism stops. These are often wrapped around a "soft" ferromagnetic core, like mild steel, to greatly enhance the field. This principle is used in various tools and devices, ranging from industrial ore separators to the components found inside a hard disk drive.