Magnetic effect of electric current is one of the major effects of electric current in use, without the applications of which we cannot have motors in the existing world. A current carrying conductor creates a magnetic field around it, which can be comprehended by using magnetic lines of force or magnetic field lines. The nature of the magnetic field lines around a straight current carrying conductor is concentric circles with centre at the axis of the conductor.
The direction of the magnetic field lines of force around a conductor is given by the Maxwell’s right hand grip rule or the right handed cork screw rule. The strength of the magnetic field created depends on the current through the conductor. If the conductor is in the form of a circular loop, the loop behaves like a magnet. If the current in the loop is in the anticlockwise direction, a north pole is formed and if the current is in the clockwise direction a south pole is formed.
A current carrying conductor in the form of a rectangular loop behaves like a magnet and when suspended in an external magnetic field experiences force. The direction of the force is given by Fleming’s left hand rule. This gives the basis for an electric motor. An electric motor essentially consists of a coil as an armature, a split ring commutator for changing the direction of the current in the coil. There are two brushes linked with the split rings that maintain the contact with the armature for the current flow. Electric motor converts electrical energy to mechanical energy.
A number of such loops form a coil and the coil is termed solenoid. If there is a soft iron core in the solenoid, it behaves like a magnet as long as there is current through the coil. Thus it is an electromagnet.
When an electric current passes through a conductor, a magnetic field is created around the conductor. This phenomenon is known as the magnetic effect of electricity.
A magnetic field is the extent of space surrounding a magnet where the magnet’s effect can be felt.
Magnetic field lines represent the lines of action of the force acting on a unit North Pole placed in a magnetic field.
Maxwell’s right hand grip rule:
If we hold a conductor in the right hand with the fingers curled around it and the thumb stretched out, then the thumb denotes the direction of the current flow and the direction of the curling of the fingers indicate the direction of the magnetic field lines.
Maxwell’s corkscrew rule:
On turning, if a right-handed corkscrew advances in the direction of current, then the direction of rotation of its head gives the direction of the magnetic field lines. A magnetic field caused by a current-carrying conductor consists of sets of concentric lines of force. The direction of the magnetic field lines depends on the direction of the current passed through the conductor.
A magnetic field caused by a current-carrying conductor consists of sets of concentric lines of force.
The direction of the magnetic field lines depends on the direction of the current passed through the conductor.
A solenoid consists of an insulated conducting wire wound on a cylindrical tube made of plastic or cardboard.
- An electromagnet is a magnet made up of a coil of insulated wire wrapped around a soft iron core that is magnetised only when current flows through the wire.
- Fleming’s left hand rule: When the forefinger, middle finger and thumb of the left hand are stretched such that they are at right angles to each other, then:
- he 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. An electric motor converts electrical energy into mechanical energy using the magnetic effect of electricity.