Effects of current electricity

Chemical effects No chemical change is taking place in metals but in an electrolyte many changes are taking place. Electrolytes are chemical substances which contains ions and capable of carrying a current in a solution. They are acids, bases, and salts.

Electrolysis Electrolysis is a decomposition of liquid compound by passing electric current through liquid called electrolyte (salt water, copper sulphate, sulphuric acid).

Chemical effects Faraday's Laws of Electrolysis First law states that the mass of a substance deposited or liberated on an electrode during electrolysis is proportional to the total quantity of electric charge passed through the electrolyte. If m is the mass of substance deposited or liberated When charge q passes m α q Or m = z q Where “z” is a constant of proportionality and is called electrochemical equivalent

Second law states that if same quantity of charge is passed through several electrolytes, the mass of substance deposited or liberated at electrodes is proportional to their chemical equivalent (equivalent weight). If m1 & m2 are masses of the substances liberated or deposited on various electrodes When same current is passed for same time through their electrolytes E1 & E2 are the chemical equivalents m1 / m2 = E1 / E2

Chemical effects One of the chemical effects of an electric current is used to define the size of the unit of current the international congress of electricians at Chicago in 1893 agreed to define the unit-current as one which deposits silver at the rate of 0.001118 grams per second. This unit is called an ampere.

Magnetic effects Electromagnetic induction The process of producing electricity by magnetic field and vice-versa It is the result of interaction between a conductor & a magnetic lines of force The factors essential for electro magnetic induction are A conductor Magnetic lines of force Relative movement

Magnetic effects A current is induced either by moving a magnet near the loop or by moving the loop near a magnet. It is the relative motion between the two which is important. Electromagnetic induction takes place because of the relative motion between a magnet and a coil. The induced current exists as long as there is a relative motion between the coil and the magnet. When the magnet is moved faster, then the amount of current induced is found to be higher.

The factors essential for electro magnetic induction. A conductor Magnetic lines of force Relative movements between the conductor and the magnetic lines of force The strength of the induced electromotive force ( force which causes electrons to move along a conductor connecting points of different potential) depends on, The rate of change of the magnetic field => high frequency of AC current gives stronger EMF. The inductance ( ability to induced a current; measured in Henries) of the conductor => use many turns of wire in the coil, placing the turns of the coil close together and winding the coil on to a soft iron core.

Maxwell's Right Hand Grip Rule If we hold the current carrying wire in our right hand in such a way that the thumb is stretched along the direction of the current, then the curled fingers give the direction of the magnetic field produced by the current.

Magnetic effects A coil of wire that carries a current could produce a magnetic field exactly like the field around a permanent magnet.

Fleming's Right Hand Rule The direction of the current in a wire moving perpendicular to itself and to a magnetic field may be found by Fleming's right hand rule. If the thumb, forefinger and middle finger of the right hand are stretched in a mutually perpendicular direction, in such a way that the forefinger directs towards the magnetic field, the thumb shows the motion of the wire, then the middle finger shows the direction of the induced current.

Lenz's Law The magnetic field of any induced current opposes the change that induces it.

Self inductance In a coil connected to a battery through a rheostat, the current through the coil produces a magnetic flux which links with the coil itself. If we vary the resistance in the circuit, the current through the coil changes and the magnetic flux through the coil also change. This change in flux indicates an EMF in the coil itself. Such an EMF is called self-induced EMF and the phenomenon is called self induction

Mutual inductance If tow coils are close together a changing current and magnetic field in one can induce a changing magnetic field and current in the other

Eddy currents (Foucault current) Induced in conductors in the presence of changing magnetic fields. It is caused when a moving (or changing) magnetic field intersects a conductor, or vice-versa. The relative motion causes a circulating flow of electrons, or current, within the conductor. It transform useful forms of energy, such as kinetic energy, into heat, which is generally much less useful. Hence they reduce the efficiency of many devices that use changing magnetic fields, such as iron-core transformers and electric motors.

Thermal effects Heat is produced in current-carrying conductors, resulting in an increase in temperature of the conducting material. The heating is a result of the collisions between the moving free electrons and the relatively stationary atoms of the conductor material.

Joule’s Law  The rate at which heat is produced in a resistor is proportional to the square of the current flowing through it, if the resistance is constant. H I2

Thermal effects Work done by an electric current 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 or W = (IR) It = I2Rt

Thermal effects 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.

Thank You..