ELECTRIC CURRENTS ELECTRIC CURRENTS AND CIRCUITSAND CIRCUITS

ELECTRIC CURRENTELECTRIC CURRENT

• The flow of electrons is called an electric current.

ELECTRIC CIRCUITELECTRIC CIRCUIT

• The unbroken path through which an electric current can flow is called an electric circuit.

ELECTRIC CIRCUIT DIAGRAMSELECTRIC CIRCUIT DIAGRAMSComponent  Component  Circuit Symbol Function of Component

Wire To pass current very easily from one part of a circuit to another.

Cell Supplies electrical energy.The larger terminal (on the left) is positive

(+). A single cell is often called a battery, but

strictly a battery is two or more cells joined together.

Battery Supplies electrical energy. A battery is more than one cell.

The larger terminal (on the left) is positive (+).

Fuse A safety device which will 'blow' (melt) if the current flowing through it

Bulb A transducer which converts electrical energy to light. This symbol is used for a

lamp providing illumination, for example a car headlamp or torch bulb.

On-Off Switch SPST = Single Pole, Single Throw.An on-off switch allows current to flow

only when it is in the closed (on) position.

HEATING EFFECT OF CURRENT HEATING EFFECT OF CURRENT

• 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'.

ELETRIC FUSEELETRIC FUSE

• In electronics and electrical engineering a fuse (from the Latin "fusus" meaning to melt) is a type of sacrificial over current protection device. Its essential component is a metal wire or strip that melts when too much current flows, which interrupts the circuit in which it is connected. Short circuit, overload or device failure is often the reason for excessive current.

• A fuse interrupts excessive current (blows) so that further damage by overheating or fire is prevented. Wiring regulations often define a maximum fuse current rating for particular circuits. Over current protection devices are essential in electrical systems to limit threats to human life and property damage. Fuses are selected to allow passage of normal current and of excessive current only for short periods.

MINIATURE CIRCUIT BREAKERMINIATURE CIRCUIT BREAKER

• A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuIt. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation.

MAGNETIC EFFECT OF MAGNETIC EFFECT OF ELECTRIC CURRENTELECTRIC CURRENT

• Major progress in understanding magnetism came after the relationship between electricity and magnetism was established by Hans Christian Oersted in 1820. He found that an electric current moves a compass needle and this effect lasts as long as the current flows through the wire. It is then possible to produce magnetism without any magnetic substance at all.

ELETROMAGNETELETROMAGNET

• Wrap a wire around a soft iron piece (known as core. When a electric current is passed through the wire, the iron piece behaves like a magnet. A magnet made using an arrangement is called an electromagnet.

ELECTRIC BELLELECTRIC BELL