Magnetic Fields and Forces: What You Need to Know

Magnetic fields and forces are important ideas in physics. They are shaped by a few key rules that explain how they work and interact with each other.

What Are Magnetic Fields?

Magnetic fields are created by moving electric charges, like when electrons flow through a wire.

You can figure out the direction of a magnetic field using something called the right-hand rule. Here’s how it works:

• Point your thumb in the direction the electric current is flowing.
• Your curled fingers will show you the direction of the magnetic field lines that wrap around the current.

These magnetic field lines start at the north pole of a magnet and loop back to the south pole.

How Magnetic Force Works

One important idea about magnetism is the Lorentz force law. This law explains the force on a charged particle (like an electron) that is moving through a magnetic field.

The force can be described with this simple formula:

$$\mathbf{F} = q(\mathbf{v} \times \mathbf{B})$$

Here’s what the letter symbols mean:

• $\mathbf{F}$ is the magnetic force.
• $q$ is the charge of the particle.
• $\mathbf{v}$ is the speed and direction of the charge.
• $\mathbf{B}$ is the strength and direction of the magnetic field.

Interestingly, the force from the magnetic field is always at a right angle to both the charge's speed and the magnetic field. This causes the charged particles to move in circles or spirals.

How Strong is a Magnetic Field?

The strength of a magnetic field is shown with the letter $B$ and is measured in units called teslas (T).

The stronger the magnetic field, the stronger the force will be on a moving charge.

Electromagnetism and Induction

Another important part of magnetism is something called electromagnetic induction. This happens when the amount of magnetic flow (magnetic flux) changes in a closed loop, which then creates an electromotive force (EMF) in that loop. This idea is usually explained by Faraday's law of induction.

You can express this law with this simple formula:

$$\text{EMF} = -\frac{d\Phi_B}{dt}$$

Here, $\Phi_B$ stands for magnetic flux.

Why Magnetism Matters

Knowing about these basic ideas of magnetism is very important for many things we use every day, like electric motors, generators, and devices that store data magnetically.

As you study more about magnetism in University Physics II, understanding these basic concepts will help you explore more complex ideas in magnetism later on.