The SI unit of inductance is the henry (H), named after the American physicist Joseph Henry. It is defined as the inductance of a circuit in which an electromotive force of one volt is produced when the current changes at a rate of one ampere per second.

The inductance of a coil is affected by several factors, including the number of turns, the length of the coil, and the cross-sectional area of the coil. Increasing the number of turns or the length of the coil increases the inductance, while increasing the cross-sectional area decreases the inductance.

The magnetic energy stored in an inductor is directly proportional to the inductance of the inductor and the square of the current flowing through it. The formula for magnetic energy is: E = 1/2 * L * I^2, where E is the magnetic energy, L is the inductance, and I is the current.

Inductance has a wide range of applications, including transformers, inductors in electronic circuits, and electric motors. Transformers use the principle of electromagnetic induction to transfer electrical energy from one circuit to another. Inductors in electronic circuits are used to store energy and filter out unwanted signals. Electric motors use the interaction between magnetic fields and currents to generate motion.

The inductance of a solenoid can be calculated using the formula: L = μ₀ * N² * A / l, where L is the inductance, μ₀ is the permeability of free space, N is the number of turns, A is the cross-sectional area of the solenoid, and l is the length of the solenoid.

Increasing the frequency of an AC current increases the inductance of a coil. This is because the higher frequency current produces a stronger magnetic field, which in turn increases the inductance of the coil.

The energy stored in an inductor is given by the formula $E = 1/2 * L * I^2$, where E is the energy stored, L is the inductance of the inductor, and I is the current flowing through the inductor.

The unit of magnetic flux is the weber (Wb). It is defined as the magnetic flux produced by one magnetic pole of strength one ampere-meter.

Magnetic flux is directly proportional to magnetic field. The formula for magnetic flux is: Φ = B * A, where Φ is the magnetic flux, B is the magnetic field, and A is the area perpendicular to the magnetic field.

Increasing the number of turns in a coil increases its inductance. This is because each additional turn adds to the magnetic field produced by the coil, which in turn increases the inductance.

Inductance and resistance are independent of each other in an AC circuit. This means that the inductance of a coil does not affect the resistance of the circuit, and vice versa.

The energy stored in a magnetic field is given by the formula $E = 1/2 * B^2 * V$, where E is the energy stored, B is the magnetic field strength, and V is the volume of the magnetic field.

Increasing the cross-sectional area of a coil decreases its inductance. This is because the magnetic field produced by the coil becomes weaker as the cross-sectional area increases.

Inductance and capacitance are inversely proportional in an AC circuit. This means that as the inductance of a coil increases, the capacitance of the circuit decreases, and vice versa.

The inductance of a toroid can be calculated using the formula: L = μ₀ * N² * r, where L is the inductance, μ₀ is the permeability of free space, N is the number of turns, and r is the mean radius of the toroid.