In the year 1820, the famous scientist Hans Christian Oersted of Denmark found that when an electric current passing through a conducting wire, the magnetic needle kept near it shows deflection. Which conclude the presence of another magnetic field. On increasing the electric current the deflection in the needle increases and on changing its direction the direction of deflection also changes. On the basis of this experiment Oersted concluded that when an electric current is passed through a conducting wire a magnetic field is produced around it and named this phenomenon as magnetic effect of electric current.
Magnetic field is the space surrounding the magnet in which the magnetic lines of force exist or in which the magnetic needle shows deflection. Magnetic lines of force are lines surrounding the magnet which travels from north pole to south pole of the magnet. They are closed and complete.
We know that magnetic field is produced when electric current flows through a conductor. But we don’t know about the direction of magnetic field. So for obtaining the direction of magnetic field two rule were formed which are as follows:
- Right Hand Thumb Rule: Just make your right-hand in thums-up gesture. Now if your thumb points in the direction of electric current then the direction in which your fingers encircle will give the direction of magnetic field.
- Maxwell’s Corkscrew Rule: If a corkscrew is driven in the direction of current passing through the wire, then the motion of the thumb shows the direction of the magnetic field.
Is Earth a magnet?
Yes, earth also acts as a magnet. The Earth’s magnetic field is supposed to arise from the electric currents in the iron rich molten core outside the solid inner core of earth.
Do human-being also have magnetic field?
Yes, Magnetic field is also present in the human body. Magnetic field in our body produced because of the weak ionic currents that flows along the nerve cells. The Magnetic Resonance Imaging(MRI) technique in medical science which is used to scan inner human body parts is based on the magnetic field present inside the body.
Force on a current carrying conductor placed in a magnetic field:
A French scientist Andre Ampere on the basis of his experiment suggested that when a current is passed through a conductor kept in a magnetic field then a force acts on it.
Direction Of Force:
Direction of a force acts on a current carrying conductor placed in a magnetic field can be easily known by Fleming’s Left Hand Rule.
Fleming’s left hand rule states that when you stretch the fore finger, the middle finger and the thumb in such a manner that all three are perpendicular to each other. If the fore finger points the direction of magnetic field and the central finger shows the direction of current then the thumb will points the direction in which conductor will move i.e. direction of force.
In the year 1831, Michael Faraday succeeded in producing current in a coil kept in the magnetic field of a moving magnet.
When a magnet is in a relative motion to a coil an electromotive force is induced between the ends of the coil, this induced emf produces the current known as induced current. This process of producing electric current is called electromagnetic induction.
It is a device which converts electrical energy into mechanical energy(rotation). Electric motor is used in electric fans, washing machines, mixer and grinder etc.
Types Of Current:
Direct Current: The current whose direction of flow remains same with time is called direct current. The current which we will get from cells and battery were direct current.
Alternating Current: The current which changes direction after equal intervals of time, is called alternating current. The electricity supplied in our houses is alternating current.
Direct Current Generator:
A device which produces direct current is called D.C. Generator or Dynamo.