Symbols of Electric Components
Symbols Of Electric Components:
A battery is defined as a combination of two or more cells. In a battery, the negative terminal of one cell is connected to the positive terminal of the next cell, and so on.
To indicate the correct place for the cells in the battery compartment, ‘+’ and ‘–’ symbols are usually printed there.
The continuous conducting path between the two terminals of a cell or battery along which an electric current flows is called a circuit.
Closed Circuit: When the key is switched on or closed the circuit is said to be a closed circuit as it is complete.
Open Circuit: When the key is switched off or opened the circuit is said to be an open circuit as it is incomplete.
In the bulb, there is a thin wire, called the filament, which glows when an electric current passes through it.
When the bulb gets fused, its filament is broken.
Connection of Cells/Battery
- ‘+’ and ‘-‘ symbols are printed in the battery in order to have an exact placement of the cells in their respective battery compartment. · The switch or key can be placed anywhere in the circuit.
- The circuit is complete and it is said to be closed only when the switch is ON.
- The circuit is incomplete and it is said to be open, only when the switch is OFF.
Heating Effect of Electric Current
When an electric current passes through a wire the wire gets heated up. This is known as the heating effect of electric current.
The heat that is produced in the wire depends upon the following factors:
- the material of the wire
- the length of the wire
- the thickness of the wire
Many appliances work on the heating effect of electric current such as:
- electric heater
- electric iron
- electric stove
- geysers
- electric coffee maker
- toaster
- hair dryer
Appliances that work on the heating effect of electric current
All these elements produce a high amount of heat when electricity passes through them. However, this amount can change depending upon the requirements of the device. This is so because they contain a coil of wire known as an element.
The filament of a bulb is a coiled wire that gets hot when electricity is passed through it. This makes the filament glow and as a result, light is produced from the bulb.
An electric fuse is a device that is used to prevent damage that can be caused by an excess of electric current. According to the heating effect of the electric current, a wire becomes hot as current is passed through it. However, if an excess of current is passed through a wire it can melt or break.
The electric fuse consists of a wire which is made up of a metal or an alloy that has a low melting point. As a result, the wire breaks down easily as a high current passes through it. As the wire breaks the circuit of the fuse opens and hence no current passes through it.
The electric fuse can prevent a short circuit for fire due to high electric current.
Different types of fuses are used for different devices and some are also available for houses as well.
- Sometimes we connect different devices to the same socket which results in drawing more current from that socket. As a result, the load on the circuit increases and it can lead to a short circuit or fire.
- When the insulation of wires gets torn away, the wires can come in contact with each other which causes a spark or may lead to a fire (short circuit).
CFL (Compact Fluorescent Lamp): CFLs do not work on the heating effect of electric current.
CFL (Compact Fluorescent Lamp):
- They do not have a filament inside them instead they contain two electrodes that produce light.
- These bulbs have a fluorescent coating inside them which makes the light brighter.
- CFLs thus save energy as they do not produce heat along with the light.
ISI stands for Indian Standards Institute which standardizes all electrical appliances.
A miniature circuit breaker or MCB is generally used instead of fuses.
A fuse breaks due to excessive current so that the circuit opens up and the damage can be prevented. However, once a fuse breaks down it cannot be used again.
MCB is a switch that turns OFF on its own when a circuit overloads. Once the problem with the circuit is rectified we can switch ON the MCB once again.
Overloading
It is a situation when too many electrical appliances are connected to a single socket, they draw an extremely large amount of current from the household circuit. The flow of large current due to overloading may heat the copper wires of household wiring to a very high temperature and a fire may be started.
Short Circuit
Electric current is supplied by the household through two insulated wires which run together and reach each and every electrical appliance. One insulated wire is called live wire and the other insulated wire is called neutral wire and both these wires are necessary for the working of an electrical appliance.
Always use proper fuses which have been specified for particular applications carrying ISI mark Never use just any wire or strip of metal in place of a fuse.
Magnetic Effect of Electric Current
When an electric current is passed through a wire it behaves like a magnet. This is called the magnetic effect of the electric current.
The magnetic effect of the electric current was discovered by scientist Hans Christian Oersted who found that when an electric current is passed in a wire, then the compass needle placed near it got deflected from its usual North-South position.
Deflection in Compass Needle due to Electric Current
The magnetic effect is increased only if we use a long coil of wire instead of a straight wire. Even further the magnetic effect is increased if the coil of wire is wound around an iron rod and then current is passed through it.
Electromagnet
A magnet whose magnetic field is generated with the help of electric current is called an Electromagnet.
The Electromagnet is formed because of the magnetic effect of the electric current.
Applications of Electromagnets
- Electromagnets are used in domestic appliances such as electric bells.
- They are used in toys.
- They are used in all kinds of telecommunication equipment.
- They are used in cranes to separate magnetic materials from junk and to lift heavy objects.
- They are used by doctors to remove any magnetic materials that we have fallen in the eye
Factors through which an electromagnet can be made stronger:
- By increasing the amount of current used in the coil.
- By increasing the number of turns forming the coil.
The magnetism of an electromagnet can be switched ON or switched OFF as desired. While it is not possible with a permanent magnet.
By increasing the number of turns in the coil and by increasing the current passing through the coil an electromagnet can be made very strong. On the other hand, a permanent magnet cannot be made so strong.
Electric Bell
Electric Bell
Components of an Electric Bell
- A coil of wire is wound over an iron piece that forms the Electromagnet.
- An iron strip has a hammer attached to it which is joined to the wire coil.
- A contact screw through which is attached to the iron strip.
- A battery that connects the wire coil and the contact screw.
- A switch in the middle of the circuit.
Working of an Electric Bell
- When the switch of the Bell is ON, an electric current flows through the coil of wire which makes the iron piece attached to it act as an Electromagnet.
- As a result, the iron piece attracts the hammer towards itself. The hammer thus hits the bell and a sound is produced.
- As the hammer move toward the iron piece, it moves away from the contact screw which breaks down the circuit.
- As the circuit breaks the wire coil stops receiving any current which makes the electromagnet lose its magnetic effect.
