# Electromagnetism issues need clearing up

In summary, the mutual inductance between two coils is related to the current in the primary coil and the number of turns on the secondary coil.
In electromagnetism, when there is an emf is induced in a secondary coil from a current flowing in a nearby primary coil (such as in a transformer), then how is the mutual inductance, number of turns of each coil, the current in the primary coil, and the emf in the secondary coil related?

From the reading that I have been doing, I think that for a single coil:
$$B = \frac{u_0NI}{2 \pi r}$$
Where the $u_0$ is the permeability of free space (I don't know how to get the proper symbol), $N$ is the number of turns, and $B$ is the magnetic field strength.

From what I have gathered from the reading, is:
$$E = -\frac{d \psi}{dt} = -L \frac{dI}{dt}$$
Where I have used $E$ for emf, and psi for the flux (I don't know how to get the convention symbol), and $L$ is the inductance of the secondary coil, however, I am unsure as to how the mutual inductance (M) is related to the inductance (L).

I think the problem is that when people speak of inductance, I am unsure what they mean the inductance of.

The reason why I am asking is that I have a question which uses this idea, but I am so close to getting it, that I would rather not post the problem in the homework section.

Last edited:
In electromagnetism, when there is an emf is induced in a secondary coil from a current flowing in a nearby primary coil (such as in a transformer), then how is the mutual inductance, number of turns of each coil, the current in the primary coil, and the emf in the secondary coil related?

From the reading that I have been doing, I think that for a single coil:
$$B = \frac{u_0NI}{2 \pi r}$$
Where the $u_0$ is the permeability of free space (I don't know how to get the proper symbol), $N$ is the number of turns, and $B$ is the magnetic field strength.

From what I have gathered from the reading, is:
$$E = -\frac{d \psi}{dt} = -L \frac{dI}{dt}$$
Where I have used $E$ for emf, and psi for the flux (I don't know how to get the convention symbol), and $L$ is the inductance of the secondary coil, however, I am unsure as to how the mutual inductance (M) is related to the inductance (L).

I think the problem is that when people speak of inductance, I am unsure what they mean the inductance of.

The reason why I am asking is that I have a question which uses this idea, but I am so close to getting it, that I would rather not post the problem in the homework section.
L, self inductance, is the ratio of induced emf in an inductor (coil) to rate of change of current in that inductor: Emf = L dI/dt

Mutual inductance relates to two coils in which a change of current in one coil induces an emf in the other. Emf = MdI/dt where Emf is the emf in the other coil.

AM

$\phi$?

## 1. What is electromagnetism?

Electromagnetism is the branch of physics that deals with the study of the interactions between electrically charged particles. It includes the study of electric fields, magnetic fields, and how they are related.

## 2. How does electromagnetism work?

Electromagnetism works by the interaction between electric charges and magnetic fields. When an electric charge is in motion, it creates a magnetic field, and when a magnetic field changes, it can create an electric current. This relationship is described by Maxwell's equations.

## 3. What are some applications of electromagnetism?

Some common applications of electromagnetism include electricity generation, electric motors, and communication technology such as radios and cell phones. Electromagnetism is also used in medical imaging, such as MRI machines, and in transportation systems like trains and elevators.

## 4. How does electromagnetism impact our daily lives?

Electromagnetism plays a crucial role in our daily lives. It allows us to use electricity to power our homes and devices, and it enables us to communicate wirelessly. Many everyday objects, such as refrigerators, televisions, and computers, rely on electromagnetism to function.

## 5. What are some common misconceptions about electromagnetism?

One common misconception about electromagnetism is that it is only relevant to electricity and magnetism. In reality, electromagnetism has a much broader scope and is also related to other fundamental forces, such as the weak and strong nuclear forces. Another misconception is that electromagnetic radiation, such as radio waves and microwaves, is always harmful to humans. While high levels of exposure can be dangerous, low levels of electromagnetic radiation are present in our natural environment and are used in many useful technologies without causing harm.

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