Magnetic Effect of Electric Current – A magnetic field is a force field that is created by magnetic dipoles and moving electric charges, and it exerts a force on other nearby moving charges and magnetic dipoles. Magnetic Field is a vector quantity because it has both magnitude and direction.
Magnetic Field Lines
A magnetic field line or lines of forces shows the strength of a magnet and the direction of a magnet’s force. It was discovered by Michael Faraday to visualise the magnetic field.
Direction of Field Lines
Magnetic field lines are directed from the south pole to the north pole inside the magnet and from the north pole to the south outside the magnet.
Strength of Magnetic Field Lines
A straight current-carrying conductor has a magnetic field in the shape of concentric circles around it. Magnetic field lines can visualise the magnetic field of a straight current-carrying conductor.
The direction of a magnetic field produced due to a current-carrying conductor relies upon the same direction in which the current is flowing.
The direction of the magnetic field gets reversed if the direction of the electric current changes.
Let Us Understand Magnetic Effect of Electric Current Using a Simple Experiment:
Suppose a straight current-carrying conductor is hung vertically, and an electric current is flowing from north to south, i.e. from up to down. In this situation, the direction of the magnetic field will be clockwise. And if the same current is flowing from south to north through the same conductor, the direction of the magnetic field will be anti-clockwise.
The direction of the magnetic field in electric current through a straight conductor can be represented by using the Right-Hand Thumb Rule.
Right-Hand Thumb rule
Assume that you are holding a straight current-carrying conductor in your right hand such that the thumb points towards the direction of the current. Then your fingers will wrap around the conductor in the direction of the magnetic field lines.
The Right-Hand Thumb rule is also known as Maxwell’s corkscrew rule. If we consider ourselves driving a corkscrew in the current direction, then the corkscrew’s direction is in the direction of the magnetic field.
Magnetic Field Due to Flow of Current through a Circular Loop
The magnetic field produced in a circular current carrying conductor is the same as that of the magnetic field due to a straight current-carrying conductor and the current-carrying circular loop will behave like a magnet.
The magnetic field lines in a current-carrying circular loop would be in the shape of concentric circles, and at the centre of the circular wire, field lines will become straight and perpendicular to the plane of the coil.
The direction of the magnetic field in a circular loop can be recognised using the Right-Hand Thumb Rule.
Magnetic Field Due to Flow of Current in a Solenoid
A solenoid is a tightly wound helical coil of wire whose diameter is smaller than its length.
The magnetic field produced by the current-carrying solenoid is similar to a bar magnet. The magnetic field produced inside a solenoid is parallel which is similar to a bar magnet. One solenoid end behaves as a south pole, and the other end behaves as a north pole.
The strong magnetic force produced by a solenoid can be used to magnetize a piece of magnetic material. The magnet so formed is known as an electromagnet.
Direct Current
- Direct Current is the unidirectional flow of electric current. The flow of current does not change periodically. In the case of direct current, the current flows in a single direction at a steady voltage.
- Direct current power is widely used in low voltage applications such as charging batteries and light aircraft electrical systems.
- A direct current can be obtained from an alternating current using a rectifier. A rectifier contains electronic elements or electromechanical elements that allow current to flow only in one direction.
- Direct current can also be converted into alternating current using a motor-generator set or an inverter.
- The direction of the magnetic field in electric current through a straight conductor can be represented by using Right-Hand Thumb Rule.
When current is passed through the conductor it will produce a magnetic effect around it, so basically the wire acts like a magnet, and it will interact with the permanent magnet you have placed next to it, this effect can be reversed by changing the direction of the current, which according to the rule changes the direction of the magnetic field produced by it.
- Magnetic field due to a moving point charge
μo ≡ 4π × 10-7 N·s2/C2 is called the permeability of free space - Biot- savart’s Law: This law states that the magnetic field (dB) at point P due to small current element Idl of the current-carrying conductor is directly proportional to the Idl (current) element of the conductor
- Magnetic field due to a straight wire
- Magnetic field due to an infinite straight line
- Magnetic field due to a circular loop
i) At centreB= μ0NI/2rii) At axis
- Magnetic field on the axis of a solenoid
B = (μ0NI/2) (cos θ1 – cos θ2) - Amperes Law
- Magnetic field due to a long cylinder
i) B= 0, r ＜ Rii) B = μ0I/2πr, r ≥ R - Magnetic force acting on a moving point charge
- Magnetic force acting on a current-carrying wire
- Magnetic Moment of a current carrying loop M = NIA
- The torque acting on a loop
- Magnetic field due to single poleB = (μ0/2π) m/r2
- Magnetic field on the axis of the magnetB = (μ0/4π) 2M/r3
- Magnetic field on the equatorial axis of the magnetB = (μ0/4π) M/r3
- Magnetic field at the point P of the magnet
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