Inductance

Power can flow through a wire.

This moving power makes a tiny magnet. The magnet does not like to change. It tries to keep the power moving at the same speed.

When the power changes, the magnet pushes back. This push helps stop the power from changing too fast. This is a special way that wires work.

Some parts use a coil of wire to help.

A coil can hold energy in its magnetic field. This makes the magnet even stronger.

We can also put metal in the middle of a coil. This helps the coil work much better. It makes the magnet very strong.

It is amazing how wires can act like magnets. This helps us use power in many ways.

Electricity can act like a magnet. When current flows through a wire, it makes a magnetic field. This field stays around the wire. If the current changes, the magnetic field also changes.

This change causes a push-back. A change in the magnetic field makes a new voltage. This is called electromagnetic induction. This new voltage tries to stop the current from changing. We call this back EMF. This push-back is called inductance.

An inductor is a part made to use this. It is usually a coil of wire. A coil has more inductance than a straight wire. This is because the magnetic field lines pass through the coil many times. You can make the magnet even stronger. You can put a metal core in the center of the coil.

This core can make the inductance much larger.

Inductance also lets us store power. The energy stays in the magnetic field. If the current stops, the field goes away. This returns the energy to the circuit.

We measure inductance in units called henries. This name honors Joseph Henry. He found these facts on his own.

Inductance is a special way that electrical conductors act. It is the tendency of a wire to resist any change in the electric current flowing through it. When current moves through a wire, it creates a magnetic field around that wire. The strength of this field depends on how much current is flowing. If the current changes, the magnetic field changes too. This change is very important because it leads to something called electromagnetic induction.

How does this work step by step? First, a current flows through a conductor and creates a magnetic field. If that current changes in size, the magnetic field also changes. According to Faraday's law of induction, this changing field creates a new voltage in the wire. This new voltage is called an electromotive force, or EMF. Lenz's law tells us that this induced voltage actually works to oppose the change that created it. This specific push-back is called back EMF.

Scientists have studied these forces for a long time. People in ancient times noticed things like lightning and magnetic rocks called lodestones. In 1831, Michael Faraday described electromagnetic induction through his own experiments. He wrapped wires around an iron ring and saw a tiny current flow when he connected a battery. He also found that sliding a magnet in and out of a coil of wires created currents. Later, in May 1884, Oliver Heaviside coined the term "inductance" to describe these effects.

There are many specific facts to know about how we measure this. We use the symbol for inductance to honor the physicist Heinrich Lenz. In the SI system, the unit of inductance is the henry (H). This unit is named after Joseph Henry, who discovered inductance on his own. One henry is the amount of inductance that causes one volt of voltage when the current changes at one ampere per second. You can build a part called an inductor to add inductance to a circuit. These are usually made of a wire wound into a coil or helix.

Inductance is linked to many things you might see in technology. An inductor stores energy inside its magnetic field. If the current increases, the energy is stored in the field. If the current decreases, the magnetic field shrinks and returns that energy to the circuit. You can also have mutual inductance. This happens when two circuits are close together and their magnetic fields overlap. This is the main idea that makes a transformer work. Even a simple coil of wire has more inductance than a straight wire because the magnetic field lines pass through the loop many times.

Inductance is a fundamental property of electrical conductors. It describes the tendency of a conductor to oppose any change in the electric current flowing through it. This phenomenon occurs because an electric current generates a magnetic field around the conductor. The strength of this magnetic field is directly tied to the magnitude of the current. When the current changes, the magnetic field changes as well. This change in the magnetic field triggers a process known as electromagnetic induction.

The mechanism of inductance follows a specific sequence of cause and effect. First, a current flows through a conductor and creates a magnetic flux. Magnetic flux is the total magnetic field passing through the circuit. If the current varies, the magnetic flux also changes. According to Faraday's law of induction, a changing flux induces an electromotive force, or EMF, within the circuit. This induced voltage is measured in volts. Lenz's law explains the direction of this voltage. It states that the induced voltage acts in a direction that opposes the change in current that created it. This specific type of voltage is called back EMF.

There are two primary types of inductance: self-inductance and mutual inductance. Self-inductance, often simply called inductance, is the effect of a conductor on itself. It is the ratio between the induced voltage and the rate of change of the current. Mutual inductance occurs when two or more circuits are located close to one another. In this case, the magnetic field of one circuit passes through the other. This allows a change in current in one circuit to induce a voltage in the nearby circuit. This principle of mutual inductance is the core mechanism behind how a transformer works.

The history of understanding these forces spans centuries. Ancient people observed static electricity and lightning, as well as magnetic attraction from lodestones. However, the scientific theory of electromagnetism was truly developed in the 19th century. In 1831, Michael Faraday first described electromagnetic induction. He used an iron ring with two wires wrapped around it to observe transient currents. He also demonstrated induction by sliding a bar magnet through a coil of wires. Later, in May 1884, Oliver Heaviside coined the term "inductance." He used it as a convenient way to refer to the "coefficient of self-induction."

We use specific units and symbols to measure and represent inductance. The symbol for inductance is often chosen to honor the physicist Heinrich Lenz. In the International System of Units (SI), the unit of inductance is the henry (H). This unit is named in honor of Joseph Henry, who discovered inductance independently of Faraday. One henry is defined as the amount of inductance that produces one volt of voltage when the current changes at a rate of one ampere per second.

Engineers use components called inductors to add inductance to electrical circuits. An inductor typically consists of a wire wound into a coil or a helix. A coiled wire has much higher inductance than a straight wire of the same length. This is because the magnetic field lines pass through the circuit multiple times, creating multiple flux linkages. The inductance of a coil is proportional to the square of the number of turns in the coil. To increase inductance even further, a ferromagnetic core can be placed in the center of the coil. A magnetic core can increase the inductance of a coil by thousands of times.

Inductance is also deeply connected to how energy is stored and moved. An inductor stores energy within its magnetic field. When current increases, charges in the circuit lose potential energy to build the magnetic field. If the current decreases, the magnetic field shrinks and returns that stored energy to the external circuit. In alternating current (AC) circuits, inductance creates a property called inductive reactance. This is the opposition an inductor offers to an alternating current. Inductive reactance increases as the frequency of the current increases. In an ideal inductor, the current lags the voltage by 90 degrees.