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Magnetic Effects of Electric Current

What will you learn

  • A compass needle is a small magnet. Its one end, which points towards north, is called a north pole, and the other end, which points towards the south, is called a south pole.

  • A magnetic field exists in the region surrounding a magnet in which the force of the magnet can be detected.

  • Field lines are used to represent a magnetic field. A field line is the path along which a hypothetical free north pole would tend to move. The direction of the magnetic field at a point is given by the direction that a north pole placed at that point would take. Field lines are shown closer together where the magnetic field is greater.

  • A metallic wire carrying an electric current has associated with it a magnetic field.

  • The field lines about the wire consists of a series of concentric circles whose direction is given by the right-hand rule.

  • The pattern of the magnetic field around a conductor due to an electric current flowing through it depends on the shape of the conductor. The magnetic field of a solenoid carrying a current is similar to that of a bar magnet.

  • An electromagnet consists of a core of soft iron wrapped around with a coil of insulated copper wire.

  • A current-carrying conductor when placed in a magnetic field experiences a force.

  • If the direction of the field and that of the current are mutually perpendicular to each other, then the force acting on the conductor will be perpendicular to both and will be given by Fleming’s left-hand rule. This is the basis of an electric motor.

  • An electric motor is a device that converts electrical energy into mechanical energy.

  • The phenomenon of electromagnetic induction is the production of induced current in a coil placed in a region where the magnetic field changes with time. The magnetic field may change due to a relative motion between the coil and a magnet placed near to the coil. If the coil is placed near to a current-carrying conductor, the magnetic field may change either due to a change in the current through the conductor or due to the relative motion between the coil and conductor. The direction of the induced current is given by Fleming's right-hand rule.

  • A generator converts mechanical energy into electrical energy. It works on the basis of electromagnetic induction.

  • In our houses we receive AC electric power of 220 V with a frequency of 50 Hz. One of the wires in this supply is with red insulation, called live wire. The other one is of black insulation, which is a neutral wire. The potential difference between the two is 220 V. The third is the earth wire that has green insulation and this is connected to a metallic body deep inside earth. It is used as a safety measure to ensure that any leakage of current to a metallic body does not give any severe shock to a user.

  • Fuse is the most important safety device, used for protecting the circuits due to short-circuiting or overloading of the circuits.