MAGNETIC EFFECT OF AN ELECTRIC CURRENT

Magnetic Effect

Magnetic effect of electric current is one of the major effects which functions as the basic principle in appliances used in various fields of activities.

The magnetic field around a current carrying conductor can be depicted by using magnetic field lines which are represented in the form of concentric circles around it.

The direction of magnetic field through a current carrying conductor is determined by the direction of flow of electric current.

Magnetic Effects of Electric Current

Magnetic effect of electric current is one of the major effects which functions as the basic principle in appliances used in various fields of activities.

The magnetic field around a current carrying conductor can be depicted by using magnetic field lines which are represented in the form of concentric circles around it. The direction of magnetic field through a current carrying conductor is determined by the direction of flow of electric current.

The Right Hand Thumb Rule also known as Maxwell’s Corkscrew Rule is known to determine the direction of magnetic field in relation to direction of electric current through a straight conductor.

As the direction of the electric current changes, the direction of the magnetic field also gets reversed. If the direction of electric current in a vertically suspended current carrying conductor is from south to north, the magnetic field will be in the anticlockwise direction.

If the current is flowing from north to south, the direction of magnetic field will be clockwise. If a current carrying conductor is held by right hand; keeping the thumb straight and if the direction of electric current is in the direction of thumb, then the direction of folding of other fingers will show the direction of magnetic field.

Magnitude of magnetic field is directly proportional to the number of turns of coil. If there are ‘n’ turns of coil, magnitude of magnetic field will be ‘n’ times of magnetic field in case of a single turn of coil.

Application of Maxwell’s Right Hand Thumb Rule

If the conductor is in the form of a circular loop, the loop behaves like a magnet.
In a circular current carrying conductor, the magnetic field is stronger near the periphery of the conductor than in the central region.

Circular Loop Shaped Current Carrying Conductor

As suggested by Marie Ampere, a current carrying conductor exerts a force when a magnet is placed in its vicinity. Similarly, a magnet also exerts equal and opposite force on the current carrying conductor. The direction of force over the conductor gets reversed with the change in direction of flow of electric current. It is observed that the magnitude of force is highest when the direction of current is at right angles to the magnetic field. If the current is flowing in an electric circuit from South to North direction and a magnetic compass is placed over the conducting wire, the needle of the compass deflects in the direction of west. This is known as SNOW rule which helps to predict the direction of magnetic field.

Fleming’s left hand rule

According to Fleming’s left hand rule, if the forefinger, middle finger and thumb of the left hand are stretched such that they are at right angles to each other, then the forefinger gives the direction of the magnetic field. The middle finger points in the direction of the current. The thumb gives the direction of the force acting on the current-carrying conductor placed in the external magnetic field.

Electric Motor

An electric motor converts electrical energy into mechanical energy using the magnetic effect of electricity. In an electric motor, a rectangular coil is suspended between the two poles of a magnetic field. The electric supply to the coil is connected with a Commutator which reverses the direction of flow of electric current through a circuit. When the electric current is supplied to the coils of the electric motor, it gets deflected because of magnetic field. As it reaches the half way, the split ring which acts as Commutator reverses the direction of flow of electric current. Reversal of direction of electric current reverses the direction of forces acting on the coil. The change in direction of force pushes the coil, and it moves another half turn. Thus, the coil completes one rotation around an axle. Continuation of this process keeps the motor in rotation.