Magnetism and Magnetic Force

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Magnetism and Magnetic Force

This lesson aligns with NGSS PS2.B

Introduction

The magnetic force emerges as a result of the electromagnetic force, stemming from the movement of charges. It's well understood that when a charge is in motion, it generates a magnetic field around itself. Thus, magnetic force can be defined as the interaction between these magnetic fields. Magnetism refers to certain phenomena arising from magnetic forces, where objects generate fields capable of repelling or attracting other objects. It represents a collective manifestation of the electromagnetic force. In this article, we will learn about magnetism and magnetic force, how to find magnetic force, properties of magnet.

What is Magnetism?

Magnetism refers to specific phenomena generated by magnetic forces, wherein objects produce fields capable of both repelling and attracting other objects. It represents a collective property derived from the electromagnetic force.

Magnet:

A magnet is characterized as an object capable of producing magnetic fields and attracting unlike poles while repelling like poles.

Properties of Magnet:

When individuals dip a magnet into iron filings, they observe the filings accumulating around the ends of the magnet due to the strongest attraction occurring at these points. These endpoints of a magnet are referred to as magnetic poles.

Magnetic poles typically occur in pairs.

When a magnet is suspended freely, it consistently aligns itself in a north-south direction. The end of the magnet pointing towards geographic north is termed the North Pole, while the end pointing towards geographic south is termed the South Pole.

What is a Magnetic Force?

When a point charge q is situated amidst both a magnetic field B(r) and an electric field E(r), the overall force on the charge q can be expressed as the combination of the electric force and the magnetic force (Felecgtric+Fmagnetic).

The magnetic force is defined as:

The interaction between two moving charges can be characterized as the influence exerted on one charge by the magnetic field generated by the other charge.

How to Find Magnetic Force?

The magnitude of the magnetic force is depend upon the charge and the extent of motion exhibited by each object, as well as their spatial separation.

Mathematically, the magnetic force can be represented as:

F=q[E(r)+v×B(r)]

This force is known as the Lorentz Force, which is the combination of electric and magnetic forces acting on a point charge due to electromagnetic fields. The interaction between the electric and magnetic fields possesses several characteristics:

The magnetic force relies on the particle's charge, velocity, and the intensity of the magnetic field it experiences. For a positive charge, the direction of the magnetic force is opposite to that of the particle's motion.
The magnitude of the force is determined by the cross product of velocity and magnetic field, denoted as q(v×B). Consequently, the resultant force is perpendicular to both the velocity and magnetic field directions, with the orientation of the magnetic field determined by the right-hand thumb rule.
In scenarios involving static charges, the cumulative magnetic force is nullified.

Magnetic Force on a Current-Carrying Conductor

Let's delve into the force exerted by a magnetic field on a straight current-carrying rod.

Imagine a rod with uniform length l and cross-sectional area A.

In this conducting rod, let's denote the number density of mobile electrons as n.

Thus, the total number of charge carriers can be expressed as nAl Where I represent the steady current flowing through the rod. We assume the drift velocity of each mobile carrier to be vd.

When this conducting rod is situated within an external magnetic field with magnitude B, the force acting on the mobile charges or electrons can be formulated as:

F=(nAI)qvd ×B

Here,

q represents the charge value of the mobile carrier.

Since nqvd also denotes the current density j, and A×∣nqvd∣ represents the current I passing through the conductor, we can express this as:

F=[(nqevd)AI]B=[jAI]B=[Il]B

Here,

l represents the magnitude vector equal to the length of the conducting rod.

Conclusion

Magnetism refers to specific phenomena generated by magnetic forces, wherein objects produce fields capable of both repelling and attracting other objects.
A magnet is characterized as an object capable of producing magnetic fields and attracting unlike poles while repelling like poles.
The interaction between two moving charges can be characterized as the influence exerted on one charge by the magnetic field generated by the other charge.
The magnetic force relies on the particle's charge, velocity, and the intensity of the magnetic field it experiences.

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