What is the difference between magnetic effect of electric current and heating effect of electric current?
All the conductors or electrical devices have some resistance, due to which current passing through it produces heat. Infact this heat may be very high so that radiations are obtained, for example: radiations from a bulb.
Electric current also have a magnetic effect with them because moving charge always produce magnetic field. It may not be very effective for the wires used in our homes, but if you make a coil, these smaller effect combines to form a magnetic moment. For example: an electromagnet.
Energy exists in various forms such as mechanical energy, heat energy, chemical energy, electrical energy, light energy and nuclear energy. According to the law of conservation of energy, energy can be transformed from one form to another.
In our daily life we use many devices where electrical energy is converted into heat energy, light energy, chemical energy or mechanical energy. When an electric current is passed through a metallic wire like the filament of an electric heater, oven or geyser, the filament gets heated up and here the electrical energy is converted into heat energy. This is known as the 'heating effect of current'.
Why is heat produced when current is passed through a wire? A metallic conductor has a large number of free electrons in it. When a potential difference is applied across the ends of a metallic wire, the free electrons begin to drift from a region of low potential to a region of high potential. These electrons collide with the positive ions (the atoms which have lost their electrons). In these collisions, the energy of the electron is transferred to the positive ions and they begin to vibrate more violently. As a result, heat is produced. The greater the number of electrons flowing per second, the greater will be the rate of collisions and so greater is the heat produced.
Mathematical Expression for Heat Produced
A potential difference is a measure of work done in moving a unit of charge across a circuit. Current in a circuit is equal to the amount of charge flowing in one second.
Therefore, the work done in moving 'Q' charges through a potential difference 'V' in a time 't' is given by
Work done = potential difference x current x time
W = VIt
The same can be expressed differently using ohm's law.
According to ohm's law V = IR
Therefore work can be expressed as
W = VIt
or W = (IR) It = I2Rt
The work done 'W' gets dissipated in the resistors as heat energy H
Thus, heat produced is directly proportional to the resistance, to the time and to the square of the current.
Application of the Heating Effect of Current
The heating effect of current is utilised in the electrical heating appliances such as electric iron, room heaters, water heaters, etc. All these heating appliances contain coils of high resistance wire made of nichrome alloy. When these appliances are connected to power supply by insulated copper wires then a large amount of heat is produced in the heating coils because they have high resistance, but a negligible heat is produced in the connecting wires because the wires have low resistance.
The heating effects of electric current is utilized in electric bulbs for producing light. When electric current passes through a thin high resistance tungsten filament of an electric bulb, the filament becomes white hot and emits light.
An 'electric fuse' is an important application of the heating effect of current. When the current drawn in a domestic electric circuit increases beyond a certain value, the fuse wire gets over heated, melts and breaks the circuit. This prevents fire and damage to various electrical appliances.
Major progress in understanding magnetism came after Hans Christian Oersted established the relationship between electricity and magnetism in 1820.
Magnetic field is a region near a magnetised body where magnetic forces can be detected.
A pictorial representation that gives the direction of the magnetic field at various points in a magnetic field is called a map of the magnetic field.
We need to understand the pattern of field lines around a straight conductor carrying current and also the direction of these field lines.
The direction of magnetic field around a current carrying conductor can be determined by using one of the laws.
The demonstration given below explains the nature of magnetic field due to a current carrying circular loop.
If a coil carrying current is suspended by thin elastic long conductors, it will align itself as the compass needle.
A solenoid is a long coil (shaped like a cylinder) containing a large number of close turns of insulated copper wire.
An electromagnet can be defined as a soft-iron core that is magnetised temporarily by passing a current through a coil of wire wound on the core.
Oersted's experiment shows that a current carrying wire exerts a force on a magnetic needle and deflects it from its usual north-south position.
An electric motor is a device which converts electrical energy into mechanical energy. A common motor works on direct current. So, it is also called DC motor.
The deflection is more if the magnet is moved faster. That is, the rate at which the current is induced is more when the magnet is moved faster.
The phenomenon of production of induced emf in one coil due to change of current in a neighbouring coil is called mutual induction.
When a straight conductor is moved rapidly in a magnetic field, then a current is induced in the conductor. It is based on the phenomenon of electromagnetic induction.
When the current flows in the same direction it is called 'direct current' or DC.The current derived from a cell or battery is unidirectional. So it is a DC source.
Electric power is usually generated at places which are far away from the places where it is consumed. At the generating station, the electric power is generated at 11,000 volts. This voltage alternates at a frequency of 50 Hz.
When the electrical appliance is switched on, the metal casing of the appliance will remain at zero potential as it is in contact with the earth wire in the three pin socket. It thus prevents us from an electric shock even if we touch it accidentally.
The phenomenon by which an emf or current is induced in a conductor due to change in the magnetic field near the conductor is known as electromagnetic induction.
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