Laws of Magnetic Force: definition, properties, and magnetism

what is magnetism?

Long ago, people thought magnetism was a kind of magic. They didn’t understand how it worked, so they didn’t use it much. But as time passed and science grew, we learned the truth — magnetism is not magic, it’s a real and powerful force.

Today, magnetism is one of the most important parts of electrical engineering. It helps run many machines we use every single day. Without magnetism, we wouldn’t have electric motors, generators, transformers, or even simple things like fans and lights.

Just think — without magnetism, there would be no radio, no television, no telephone, and no internet. Cars, airplanes, and trucks wouldn’t start. We would lose many of the comforts and tools we now take for granted.

Magnetism is all around us, even though we cannot see it. It helps turn energy into motion. It makes machines work quietly and smoothly. It connects cities and people across the world.

In this chapter, we will explore the most important features of magnetism. You will see how this invisible force makes our world brighter, faster, and better.

magnet poles explained

Have you ever played with a magnet and noticed how it pulls things like nails or paper clips? Try dipping a bar magnet into iron filings. What do you see? Most of the filings stick to the two ends of the magnet. These ends are very special. They are where the magnet is the strongest. We call these ends the poles of the magnet.

🧲 definition: magnetic poles

Every magnet has two poles:

• North Pole (N)
• South Pole (S)

These poles are not just names. They show where the magnetic force is the strongest.

🧭 find magnet poles

To find which end is the north and which is the south:

1. Take a bar magnet.
2. Tie a thread at its middle and hang it freely.
3. The magnet will slowly turn and settle in one direction.

The end that points towards the Earth’s North is called the North Pole, and the other end is the South Pole.

🔍 Important Facts About Magnetic Poles

Let’s understand some very interesting things about magnets:

1. Poles Cannot Be Separated

If you break a magnet into two pieces, you won’t get just a north or a south pole. Instead, each piece becomes a new magnet, with its own north and south poles. You can break it again and again, and still, each piece will have both poles.

2. Both Poles are Equal

The North and South poles are equally strong. They pull with the same power. This power is called pole strength.

3. Like Poles Repel, Unlike Poles Attract

• North + North → Push away (Repel)
• South + South → Push away (Repel)
• North + South → Pull together (Attract)

This is why magnets can either stick together or push apart depending on which poles face each other.

Laws of Magnetic Force

Have you ever played with magnets and felt them pull together or push away from each other? That invisible push or pull is called magnetic force.

A long time ago, a scientist named Charles Coulomb from France noticed something interesting. When he placed two magnetic poles near each other, they either pulled together or pushed apart. He became curious and started doing many experiments. After studying the way magnets behave, he made two simple rules. These rules are called Coulomb’s Laws of Magnetic Force.

What Did Coulomb Discover?

Coulomb said that:

1. Like poles repel each other – If you bring two north poles (N-N) or two south poles (S-S) close together, they will push away from each other.
2. Unlike poles attract each other – If you bring a north pole and a south pole (N-S) near, they will pull towards each other.

These rules help us understand how strong the force is and what direction it acts in.

This simple idea is the heart of the Laws of Magnetic Force.

What Are Magnetic Poles?

Magnetic poles are the ends of a magnet where the magnetic force is the strongest. But here’s something amazing: we can never find just one pole alone. Magnets always have two poles – a north pole and a south pole – and they always come together.

Even if you cut a magnet in half, both pieces will still have a north and south pole. It’s like they are always together, no matter what!

Can We Create a Single Pole?

It’s not possible to get a single, isolated magnetic pole in nature. But in experiments, scientists try to get as close as they can. For example, if we take a long, thin steel rod and put small steel balls at both ends, then magnetize it, the north and south poles mostly stay at the steel balls. In this way, we can pretend the poles are single or point-like for simple study.

Of course, Pranjul! Here’s a short summary and a detailed explanation of your text:

(i) Like poles repel, unlike poles attract

Have you ever tried to bring the same sides of two magnets close to each other? They push away, don’t they? That’s because like poles repel each other. For example, north repels north, and south repels south. On the other hand, unlike poles attract each other. North and south stick together like best friends. This is the first and most basic of the Laws of Magnetic Force.

(ii) Strength and distance affect the force

The second law says that the force between two magnetic poles depends on two things:

• How strong the poles are, and
• How far apart they are.

The stronger the magnets, the more powerful the pull or push. But the farther they are from each other, the weaker the force becomes. It’s just like trying to hear someone—when they’re close, it’s easy, but when they’re far, the sound fades.

This law is written using a simple formula:

“F ∝ (m₁ × m₂) / d²”

This means that the force (F) is directly proportional to the multiplication of their pole strengths (m₁ and m₂), and inversely proportional to the square of the distance (d) between them.

Mathematical Form of Laws of Magnetic Force

If we want to write the Laws of Magnetic Force more clearly using a constant, we get:

“F = (K × m₁ × m₂) / d²”

Here, K is a constant. Its value depends on the medium around the magnets (like air, water, or glass). In air or vacuum, this formula becomes even more specific:

“F = (m₁ × m₂) / (4π × µ₀ × d²)”

Where:

• F is the magnetic force in newtons (N)
• m₁ and m₂ are the pole strengths in weber (Wb)
• d is the distance in metres
• µ₀ is the permeability of air, which is a constant = 4π × 10⁻⁷ H/m

This is the full form of the Laws of Magnetic Force in air. If the medium is not air, we also add the relative permeability (µᵣ) of that material:

“F = (m₁ × m₂) / (4π × µ₀ × µᵣ × d²)”

This formula helps us understand how the Laws of Magnetic Force work in different environments.

What is the Unit of Pole Strength?

To understand the unit of pole strength, let’s begin with a very simple idea.

Pole strength means how strong a magnetic pole is. Just like electric charges push or pull each other, magnetic poles also repel or attract each other. This push or pull between magnetic poles is explained by the Laws of Magnetic Force.

🌟 Definition of Unit Pole Strength

The unit of pole strength is 1 weber (Wb).

But what does that mean?

Imagine you have two magnetic poles, both having the same strength. You place them 1 meter apart in air. If they push each other with a force of 62800 newtons, then each pole has a strength of 1 weber.

In simple words:

A pole of unit strength (1 Wb) is that pole which, when placed 1 meter away from another identical pole in air, pushes it with a force of 62800 N.

🧲 How do we find this using the Laws of Magnetic Force?

Let’s understand this using the formula from the Laws of Magnetic Force:

“F = (μ₀ / 4π) × (m₁ × m₂) / d²”

Where:

• F is the force between the poles
• μ₀ is the permeability of free space (μ₀ = 4π × 10⁻⁷)
• m₁ and m₂ are the strengths of the poles
• d is the distance between them

Now, put the values:

• F = 62800 N
• m₁ = m₂ = m
• d = 1 m

So:

“62800 = (4π × 10⁻⁷ / 4π) × (m × m) / (1)²”
“m² = 62800 × 1”
“m = ±1 weber”

This proves that the unit of pole strength is 1 Wb, according to the Laws of Magnetic Force.

📘 Vector Form of the Formula

In vector form, the Laws of Magnetic Force are written as:

“F⃗ = (μ₀ / 4π) × (m₁ × m₂) / d² × 𝑑̂”

Where 𝑑̂ is the unit vector showing the direction of the force.

Magnetic Field Explained

Have you ever played with a magnet? When you bring it near tiny bits of iron or another magnet, something magical happens — they pull or push each other. But what is this invisible force? It’s called a magnetic field, and it follows the Laws of Magnetic Force.

🌟 What is a Magnetic Field?

Just like how a charged object has an electric field around it, a magnet has a magnetic field around it. This is the space around the magnet where magnetic things feel a force.

If we place a magnetic pole (like the north or south end of a magnet) near another magnet, it feels a force. This happens because of the Laws of Magnetic Force.

👉 The magnetic field is strongest near the poles of the magnet and becomes weaker as we move away from it.

🧲 properties magnetic lines

We can’t see the magnetic field, but we can imagine it using magnetic lines of force. These are invisible lines that show us the path along which a north pole would move.

According to the Laws of Magnetic Force:

• Magnetic lines start from the N-pole of a magnet.
• They go through the air or surrounding material.
• They enter the S-pole, and inside the magnet, they go from S-pole back to N-pole.
• These lines form closed loops, and that’s why we call it a magnetic circuit.

Even though these lines are imaginary, they help us understand the Laws of Magnetic Force and how magnets behave.

magnetic lines of force

Magnetism is a special power that works even though we can’t see it. Just like the wind moves without being seen, magnetism flows through space around a magnet. The paths this invisible force takes are called magnetic lines of force.

These lines don’t move randomly. They follow a set of simple but powerful rules. Let’s understand the main properties of magnetic lines of force in the most easy and natural way.

✅ 1. Magnetic Lines Always Form Closed Loops

The first rule is very clear — each magnetic line of force makes a full loop. Outside the magnet, the line starts from the north pole and goes to the south pole. But it doesn’t stop there — it keeps moving inside the magnet and comes back to the north pole again. So it makes a complete round trip. It never breaks in the middle.

✅ 2. Magnetic Lines Never Cross Each Other

Another strong rule is this — no two magnetic lines ever cross. If they did, the magnetic force would pull in two different directions at one point, and that’s not possible. So, the lines stay in their own lanes, just like cars on a smooth road.

✅ 3. Close Lines Mean Strong Magnetism

When you look at the lines near a magnet, you’ll see some are close together, and some are far apart. What does that mean? When lines are close, the magnetic field is strong. When they’re spaced out, the field is weak. So, the tightness of the lines shows how powerful the magnetic force is in that area.

✅ 4. Lines Pull and Spread at the Same Time

This is a beautiful thing about magnetic lines — they try to shrink in length (like they are pulling themselves) and spread out sideways. This natural shape helps them keep balance and work smoothly. You can think of them like tiny stretched rubber bands that want to come back to their normal shape.

✅ 5. Magnetic Lines Prefer Magnetic Materials

Magnetic lines are attracted to magnetic things, like iron. They like going through such materials more than passing through non-magnetic things like air, wood, or plastic. So if there’s a piece of iron nearby, the lines will choose to move through it. This helps in designing motors, machines, and electric tools.

Magnetic Flux Explained Simply

Have you ever played with a magnet and noticed how it pulls things like pins or nails without even touching them? That invisible pulling power comes from something called a magnetic field. Now imagine the magnetic field has tiny invisible lines inside it. These are called magnetic lines of force.

When we count how many of these lines are present, we get something very important. We call it Magnetic Flux.

🌟 What is Magnetic Flux?

Magnetic Flux is the total number of magnetic lines of force passing through a magnetic field. Just remember:
More lines = More magnetic flux = Stronger magnetic field.

It’s like counting how many invisible ropes are pulling things in. The more ropes (lines), the stronger the pull.

🌟 How Do We Show Magnetic Flux?

We use a special symbol to show magnetic flux. It looks like this: φ (phi).
This Greek letter helps scientists and engineers talk about magnetic flux easily.

So, if a magnet gives out m units of flux, we say:

👉 φ = m weber

Yes, the unit of magnetic flux is called a weber (written as Wb).

🌟 Let’s Make it More Fun with Numbers!

Just like 1 meter has 100 centimeters,
1 weber = 100,000,000 magnetic lines of force!
That’s a huge number, right?

But sometimes we deal with smaller magnets. So we use a smaller unit:

👉 1 microweber (µWb) = 0.000001 Wb = 100 magnetic lines

Even tiny magnets have real power!

🌟 Can We Ever See a Single Magnetic Pole?

In science, there’s something interesting. We can’t find a North Pole alone — it always comes with a South Pole. But when we use a small compass needle, the pointed end acts almost like an isolated North Pole. It shows us the direction of the magnetic field, which always flows from North to South outside the magnet.

🌟 Why is Magnetic Flux Important?

Magnetic flux helps us:

• Understand how strong a magnet is
• Design motors, transformers, and machines
• Work with electricity in a smart and safe way

Without knowing about magnetic flux, it would be hard to build the cool things we use every day — like fans, speakers, or even mobile phones!

✅ In Short – Magnetic Flux Means…

• It’s the total number of invisible magnetic lines.
• More lines = more magnetic strength.
• It is written as φ (phi) and measured in webers (Wb).
• Tiny magnets use microwebers (µWb).
• Magnetic flux helps us understand and use magnets in real life.

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