Question

How much energy is stored in a magnet?

Answer 1

Explanation:

The magnetic field is the area around a magnetic material or a moving electric charge where the force of magnetism acts.

Therefore,

1. When a material is magnetized, it absorbs energy. This energy is stored in the magnet's field.
2. A permanent magnet or an electromagnet can produce a magnetic field.
   

The electromagnet's magnetic field energy is:

$E=(½)L{I}^2$, Where, $E$ is the energy in Joules, $L$is the inductance in Henries, $I$ is the current in Amps

$L=\frac{{\mu }_o{N}^{2}A}{l}$, Where, ${\mu }_o$ is the magnetic permeability, $N$ is the number of turns of the coil, $A$ is the cross-sectional area of the coil, $l$ is the effective length of the coil.

So,

$$\begin{gathered} I=\frac{H.l}{N} \\ I=\left(\frac{B}{\mu o}\right)\left(\frac{l}{N}\right) \end{gathered}$$

Where, $H$ is the magnetizing force., $N$ is the number of turns., $l$ is the effective length of the coil., $B$ is the magnetic field.

Therefore, $E=\frac{(½)B^{2}Al}{2{\mu }_o}$

1. The energy stored in the magnetic field of a permanent magnet can be calculated by calculating the area under the B-H curve.
2. The area under the curve represents the amount of energy stored per unit volume of the magnet.
3. The magnetic flux density is denoted by B, while the magnetic field strength is denoted by H.

Hence, this much energy is stored in a magnet.