Electric components symbols and circuit diagrams

Electric Current and its Effects

• Electric components are represented by symbols for convenience
• Electric circuits are represented by circuit diagrams using these symbols

Symbols of Electric Components

• Common electric components can be represented by symbols in circuit diagrams
• Symbols for electric components may vary across different books, but this book uses specific symbols

Electric Cell Symbol

• The symbol for an electric cell includes a longer line and a shorter, thicker parallel line
• The longer line represents the positive terminal, and the shorter, thicker line represents the negative terminal

Switch Symbols

• The 'ON' position of a switch is represented by a specific symbol
• The 'OFF' position of a switch has its own distinct symbol

Wires in Circuits

• Wires connecting components in a circuit are represented by lines

Battery Symbol

• A battery and its symbol are shown
• A battery consists of two or more cells connected together
• Inside devices, cells might be placed side by side, connected by thick wires or metal strips
• These connect the positive terminal of one cell to the negative terminal of the next
• Correct cell placement in a battery compartment is indicated by '+' and '-' symbols
• A combination of two or more cells is called a battery

Cell Holders

• Cell holders can be made using a wooden block, iron strips, and rubber bands
• When placing cells, the positive terminal of one cell must connect to the negative terminal of the next

Heating Effect of Electric Current

• When an electric current passes through a wire, the wire gets hot
• This is known as the heating effect of electric current
• Examples of electric appliances that use the heating effect of electric current include electric room heaters and cooking heaters
• These appliances contain a coil of wire called an element, which becomes red hot when electricity is passed through them
• Electrical appliances like immersion heaters, hotplates, irons, geysers, electric kettles, and hair dryers have elements inside them

Factors Affecting Heat Production

• The amount of heat produced in a wire depends on its: Material Length Thickness
• Wires for electric circuits don't normally get hot
• Elements of some appliances get so hot they're visible

Incandescent Bulbs

• Incandescent bulbs are often used for lighting, but they produce heat
• This means part of the electricity consumed is used in producing heat, which is undesirable and results in wasted electricity

Energy-Efficient Lighting

• Fluorescent tube-lights and compact fluorescent lamps (CFLs) are more electricity-efficient lighting sources
• Light emitting diode (LED) bulbs are increasingly used because they consume less electricity for a given light intensity
• LED bulbs are electricity efficient and therefore being preferred

ISI Mark

• It's recommended to use electrical appliances and gadgets that are electricity efficient
• The Bureau of Indian Standards (BIS) assigns a Standard Mark on products, called the ISI mark that provides assurance of conformity to specifications

Disposing of CFLs

• Note: Fluorescent tubes and CFLs contain mercury vapor, which is toxic
• Damaged fluorescent tubes and CFLs need to be disposed of carefully

Electric Fuses as a Safety Device

• When an electric bulb gets heated to a high temperature, it starts glowing
• If a large current passes through a wire, the wire may become so hot that it may even melt and break
• Wires made from some special materials melt quickly and break when large electric currents pass through them
• These wires are used for making electric fuses
• Fuses are inserted in all electrical circuits to prevent fires and damage to electric appliances
• There is a maximum limit on the current allowed to flow through a circuit safely
• If the current exceeds this limit, the wires may overheat and cause a fire
• A proper fuse will blow off and break the circuit in such events
• A fuse is a safety device
• One reason for excessive currents in electrical circuits is the direct touching of wires, which can happen if the insulation on the wires has come off due to wear and tear, this causes a short circuit
• Another reason is connecting multiple devices to a single socket, causing an overload

Circuit Breakers

• Miniature circuit breakers (MCBs) are used increasingly in place of fuses
• MCBs are switches that automatically turn off when the current in a circuit exceeds the safe limit
• They can be turned on to complete the circuit again
• It is always important to use proper fuses specified for particular applications

Magnetic Effect of Electric Current

• Compass needle gets deflected when a current flows in a nearby wire
• When electric current passes through a wire then it acts like a magnet
• A scientist called Hans Christian Oersted noticed the deflection of a compass needle every time current passed through the wire

Electromagnets

• When electric current passes through a wire, it behaves like a magnet
• Take an insulated wire and winds around the nail in the form of a coil. Then to connect the free ends through a cell to terminals with a switch. This behaves like a magnet
• Such coils are called electromagnets
• When the electric current is switched off, the coil loses its magnetism
• Electromagnets can be made very strong to lift heavy loads
• Electromagnets are also used to separate magnetic material from junk
• Doctors use tiny electromagnets to take out small pieces of magnetic material that have accidentally fallen in the eye
• Many toys have electromagnets inside them

Electric Bell

• Electric bell is familiar
• It has an electromagnet in it
• Electric bell contains a coil of wire wound on an iron piece
• This acts like an electromagnet
• When the iron strip is in contact with the screw, the current flows through the coil, which then pulls the iron strip
• The hammer at the end of the strip strikes to produce a sound
• Then the electromagnet pulls the iron strip, which then also breaks the circuit and the process gets repeated

Learn about electric components and their symbols for circuit diagrams. Understand the symbols for electric cells, switches in the 'ON' and 'OFF' positions, connecting wires, and batteries consisting of multiple cells.