Physics

Points To Be Remember
♦ A freely suspended magnet always stays north–south.
♦ The region around a magnet in which its magnetic force can be detected is called the magnetic field.
♦ Magnetic field is represented by magnetic field lines.
♦ The tangent at any point of a magnetic field line represents the direction of magnetic field at the point.
♦ The number of lines of force passing through a unit area represents the strength of the field. If the lines of force are closer, the magnetic field is stronger.
♦ The magnetic field lines around a current–carrying straight conductor are concentric circle around the conductor.
♦ The direction of magnetic field due to a current–carrying straight conductor is given by Fleming’s right–hand rule.
♦ The magnetic field due to a current–carrying solenoid is similar to that of a bar magnet. The magnetic field inside a solenoid is nearly uniform and is parallel to the axis of the solenoid.
♦ A magnet formed due to the magnetic field of a current is called an electromagnet. An electromagnet essentially consists of a soft iron core wrapped around with an insulated copper wire coil.
♦ An electric motor is a device that converts electrical energy into mechanical energy. It is based on the principle that : When a current carrying coil is placed in a magnetic field, a torque acts on it.
♦ When a conductor moves perpendicular to a magnetic field, an emf is induced across its ends. The direction of induced emf or the induced current is determined by the Fleming’s right–hand rule.
♦ Generator is based on the principle of electromagnetic field, with a continuous change in flux due to which an emf is induced.
♦ Power is transmitted from the power station to cities at high voltage and low current to minimize power loss.
♦ A fuse is a wire of high resistance and made up of a material of low melting point.