Current-carrying Circular Loop

A magnet is a substance that has the power to induce a magnetic field because of which it either draws or repels other magnetic substances around it. You can always find two poles, i.e., a north and a south pole, in a magnet. These poles remain together, but they have the property of attracting or repelling other substances or materials around them. On the free suspension of a magnet, its north pole always points to the geographic north pole of the earth. Before we go deeper into the topic and uncover the facts about a current-carrying circular loop, let’s have a look at a few common terms like magnetic field lines and solenoid. 

Body 

What is a magnetic field? 

When any magnetic dipole or moving electric charge exerts a kind of force on another magnetic dipole or moving electric charge, it leads to the formation of a magnetic field. A magnetic field is a vector quantity with both direction and magnitude that can be found around the magnet. The capital letter “B” denotes the magnetic field, and its SI unit is Ns/Cm or Tesla (T). 

What are magnetic field lines? 

The imaginary lines drawn around the magnet can form a shape of continuous closed loops called magnetic field lines. When we draw a tangent to the magnetic field line at any of the points, it directly represents the direction of the total magnetic field. Here are a few important facts about the nature of magnetic field lines. 

Magnetic field lines always have an originating as well as a terminating point. Inside the magnet (for instance, a bar magnet), the lines always start from the south pole and move to the north pole. Alternatively, outside the magnet, the line follows a reverse path. They start from the north pole and terminate at the south pole.

There is a way to determine the strength of the magnetic field. That is, the closer or congested the magnetic field lines are, the stronger is the magnetic field. Using this concept, we can say that the poles of the magnet where there are congested magnetic field lines have strong magnetic fields. 

Properties of magnetic field lines 

• Magnetic field lines never intersect or cross each other
• The depth of the magnetic field lines is an indicator of the power of the magnetic field
• Often, the lines start from the north pole and terminate at the south pole

Right-hand thumb rule

A magnetic field is produced in a current-carrying conductor when current is passed through it. There are different concentric circles or loops at different points of the current-carrying circular loop. To find the direction of the magnetic field, there is a rule that is commonly used. The right-hand thumb rule, also known as the Maxwell-Corkscrew rule, gives the relation between the direction of the magnetic field and the direction of the electric current that is passed through it. 

The right-hand thumb rule states that “when we hold a current-carrying conductor in our right hand with the thumb straight, the direction of the thumb represents the direction of the electric current flowing through it and the curl of the fingers represents the direction of the magnetic field in it. 

Factors that affect the strength of the magnetic field at the center of the loop

For any current-carrying circular loop, three major factors affect its magnetic field strength. These are the amount of the electric current flowing through it, the radius of the circular loop, and the number of turns in the circular loop. Here is how these three major factors affect the magnetic field strength or intensity. 

Amount of current flowing through the loop: When the amount of electric current flowing through the loop increases, the deflection of the magnetic needle also increases. Thus, indicating that the strength of three major magnetic field lines has been increased. 

Radius of the circular loop: With the increase in the radius of the current-carrying circular loop, the strength of the magnetic field decreases. Meaning the two quantities are inversely proportional to each other. For this reason, the strength of the magnetic field is less in the circular loop with a larger radius and vice versa. 

Number of turns in the coil: The magnetic field strength and the number of turns in the coil are directly proportional to each other. When one of them increases, the other automatically gets stronger and higher. This is because the current in each loop has a similar direction. This, in turn, leads to the addition of magnetic fields, and hence it gets higher with the increase in the number of turns. 

Magnetic field due to a current in a solenoid: A solenoid is made up of insulated copper wire wrapped in the shape of the cylinder. It is quite similar to the shape of a bar magnet with two endpoints behaving as north and south poles, respectively. At the inner points of the solenoid, all the lines are parallel that indicate the same strength of the magnetic field at each point. One of the common usages of the solenoid is that it is used to magnetize the materials. The materials that are placed inside it are magnetized by the strong magnetic field, and hence they are known as electromagnets. 

Conclusion 

To produce a magnetic field in a current-carrying circular loop, an electric current is passed through it. And to find the direction of the magnetic field, the right-hand thumb rule is used. The same rule is applied to find the magnetic field at other sections of the loop. Usually, the center of the loop has a combination of straight lines passing through it. The direction of magnetic field lines at the center point is at right angles to the place of the coil.