Magnetic effect of electric current-Overview

We all heard about the attractive nature of the magnet, and we know that the magnet has the property of attracting ferromagnetic materials such as iron, nickel, steel, and cobalt.  

The attractive force exerted by the magnet is called the magnetic field. 

Now, in this blog, You going to read about the magnetic effect of electric current

Normally electric current has three effects

1. Heating effect
2. Chemical effect
3. Magnetic effect

What is the magnetic effect of electric current

The flow of electric current in a conductor with the properties of magnetism is called the Magnetic effect of electric current. It is observed through the deflection of a magnetic needle in a magnetic compass. In physics, they say electromagnetic effect(Electricity + magnetism).

Why it is not possible to feel the magnetic effect of the current-carrying wire?

A current-carrying wire behaves like a magnet, but we cannot feel its effect because the strength of the magnetic field is very weak. 

Why we have to study the magnetic effect of electric current?

The magnetic effect of the current is used in many devices. Electromagnetism playing one of the major roles in modern technology. So from my point of view electromagnetism is one of the main fields.

History of the magnetic effect of current 

 When we dig deep into history, the physicist and chemist Hans Christian oersted (1777-1851) discovered the magnetic effect of current by identifying the relationship between electricity and magnetism with the help of a magnetic compass. 

He was one of the leading scientists of the 19th century and gave lectures on the topic of physics and chemistry, which were very popular among the general public. 

In April 1820, during the preparation of his lecture, he accidentally noticed a small deflection in the magnetic compass next to the current-carrying conductor. 

Surprised to see it, he did an experiment by placing a compass needle underneath a current-carrying wire and turned on the electric current. The needle of the compass showed deflection.

 Through a series of experiments,  Hans Christian oersted proved that electricity creates a magnetic field and they were interconnected. He also mentioned that the moving charges of the current create a magnetic field around the conductor. After his experiment came the modern study of "electromagnetism".

How can we know the shape of the magnetic field line?

 We can know the shape of the magnetic field line by using iron fillings and a magnetic compass.

Iron filling

If we put the iron particles around the bar magnet it will be circular.

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Magnetic field line

In the current-carrying conductor magnetic field propagates through space in the form of a concentric circle. The magnetic field is invisible, so it can be represented by diagrammatic or imaginary lines. That is called a magnetic field line.

The magnetic field lines are in the clockwise or anticlockwise direction depends on the direction of current as shown in the figure below,

Magnetic flux

The magnetic field lines passing through a unit area are called Magnetic flux.

The amount of magnetic lines crossing the closed surface area is called magnetic flux. This magnetic flux relates the magnetic  field and area, so the formula can be written as

B = Magnetic field line

A = Surface area of the closed conductor

фʙ= Magnetic flux

SI unit of the magnetic field

In some cases, we need to measure the magnetic effect of a coil. The SI unit magnetic field line is measured in the tesla (T). 

1 T(tesla) = 10 kG = 10,000 gauss 

Did you know?

Earth's magnetic field measures only 50 microTesla but bar magnet measurement is 0.01 T.

How to find the direction magnetic field line right-hand thumb rule?

The magnetic field line has a certain direction that is clockwise or anti-clockwise.  The direction of magnetic field lines depends on the direction of the current flow. The direction of the electric current plays an important role in identifying the direction magnetic field.

We can follow a small and simple rule to find the direction of the magnetic field line it's called Maxwell's right-hand thumb rule.

Maxwell right-hand thumb rule

• The right-hand thumb indicates current &
• Closed fingers direction indicates the direction of the magnetic field 

As the current flows in an upward direction the magnetic field lines form in an anti-clockwise direction. 

In a downward direction, the magnetic field lines are in opposite direction.

The magnetic field in a straight wire

The below image helps you to understand more about the magnetic field in a straight conducting wire.

The magnetic field in straight wire forms a concentric circle around the wire and the strength of the magnetic field is weak.

The magnetic field in a circular loop

We cannot experience the magnetic effect of the current. If we need a strong magnetic field, we need a large amount of current. The magnetic field strength change based on the distance from the wire. The magnetic field strength near the wire is high. Greater the distance the weaker the strength. 

 From this, we can understand that the magnetic field is directly proportional to the current and inversely proportional to the distance from the wire.

Strength of the magnetic field in a circular conductor

The magnetic field at the center of the circular wire is strong. In other words, for circular wire, the magnetic field is very much stronger than the straight wire. All magnetic field lines add up at the center and make the magnetic field stronger.

We already know that the strength of the magnetic field line is strong is directly proportional to the amount of current in the wire. Like that strength of the magnetic field, the line is directly proportional to the number of turns.

By the condition, if we increase the number of the loop then the magnetic field at the center of the loop is increased because more loop carries more amount of current. 

The polarity of the circular loop

The current carrying circular wire behaves like a thin disc magnet. One side of the disc magnet is the north pole and the other side is the south pole. 

So if the current flows in the circular loop then one side of the loop act as the north pole and another side of the loop act as the south pole.

Using the clockface rule we can easily identify the polarity of the magnetic effect of the current.

• If the observer stands in front of the circular conductor and looks at the flow of electric current in a clockwise direction, it is a south pole.

• If the same observer stands behind the same circular conductor and sees the flow of electric current in the anticlockwise direction, it is a north pole.

The magnetic effect in the solenoid

The solenoid is a cylindrical coil of wire acting as a magnet when carrying an electric current. The shape of the solenoid looks like a spring. It has an 'n' number of circular turns. So the magnetic field will be highly strong when the current flows in that circular loop.

The shape of the magnetic field in the solenoid

The shape of the magnetic field is similar to the magnetic field in the bar magnet. The bar magnet has two poles north pole and south pole. From this, we can understand that the solenoid also has two polarities (north and south pole).

how do we determine which end of the solenoid is the north pole and which end of the solenoid is the south pole? The solenoid also has many circular loops. So we can use the same clock face rule to determine the north and south poles in the solenoid.

• If the observer stands in front of the solenoid and looks at the flow of electric current in a clockwise direction, it is a south pole.

• If the same observer stands behind the same solenoid and sees the flow of electric current in the anticlockwise direction, it is a north pole.

overview

Magnetic fields are in the concentric circle for straight and circular loop current-carrying wire.

The magnetic field outside the solenoid looks like a bar magnet's magnetic field but inside the solenoid, the magnetic lines are straight and parallel

Magnetic field line & their properties

1. Magnetic field lines are closed and continuous curves travel from the north pole to the south pole.
2. The magnetic field lines come closer to one another but never intersect with each other.
3. The tangent line provides the direction of the magnetic field direction at a given point to the magnetic field lines.
4. The strength of the magnetic field is determined by the number of magnetic field lines.

Application of magnetic effect of current-carrying wire

Some of the applications are,

1. Electric bell
2. Crane lifting
3. iron junk
4. MRI Machine 
5. Maglev train