Electric Current and its Effects
An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields.
A simplified conventional pictorial representation of an electrical circuit, using standard symbols for electric components, is called a circuit diagram. A 'circuit diagram' is also known as an electrical diagram, wiring diagram, elementary diagram or electronic schematic.
A closed path formed by the interconnection of electrical components through which electric current flows is called an electrical circuit.
For a bulb to glow, it must be connected to battery rather than a cell, because a bulb will require more power. So if a circuit requires more power, then a battery should be connected.
If current does not flow through a circuit, then it is said to be an 'open' circuit or incomplete. Its switch is in 'off' position.
A circuit is said to be a closed circuit or complete when current flows through it. Its switch is in 'on' position.
A compartment that holds two or more cells together to form a battery is called a cell holder.
A combination of two or more cells connected together is called a battery. It is formed by connecting the positive terminal of one cell to the negative terminal of another. To identify the positive and negative terminals, they are denoted as + and -, respectively. These batteries are used in many devices, such as torch lights, mobile phones, calculators and even automobiles.
Different symbols are used to represent different components of electrical circuits, but the symbols used must be standardised. These symbols are easy to understand, remember and draw.
Heating Effect of Electric Current
In the 19th century, James Joule studied a property, which says that "when an electric current flows through the filament of a bulb, it generates heat, and so the bulb becomes hot". This property is named the heating effect of electric current.
Compact Fluorescent Lamps (CFL's)
We use electric bulbs to obtain light. Due to the heating effect, some part of the energy received by the bulb is used up, and hence, some electricity is wasted. CFL's do not depend on the heating effect of electricity to produce light, since they do not use filaments. Using CFL's instead of ordinary bulbs minimises wastage of electricity. In CFL's, light is generated using two electrodes. The fluorescent coating inside each tube makes the light brighter.
We use every day many appliances that work on the property of the heating effect of electric current. For example, the electric room heater, electric roti maker, electric iron, toaster, hair dryer, electric stove, immersion water heater, food warmer, electric coffee maker, electric rice cooker and geyser work on the property of the heating effect of electric current.
These appliances have coils of wire that produce heat, which are known as heating elements. As current flows through these electrical appliances, the coils of wire inside turn bright orange red in colour. This is because a huge amount of heat is produced. Different appliances have different types of heating elements. The type of heating element depends on the function of the appliance. Some appliances are required to produce more heat than others.
You should purchase only appliances that bear an ISI mark. ISI stands for Indian Standards Institute. If an appliance bears the ISI mark, it means that it is safe and will not waste electrical energy. Moreover, it is a mark of quality.
Factors affecting production of heat:
The factors that affect the production of heat in a wire through which an electric current is passing are the length and thickness of the wire, the duration of flow of current, and the material of the wire.
The electric fuse works on the principle of the heating effect of electric current. An electric fuse is a safety device to prevent damage to an electrical circuit when excessive current flows through it. It is made of a special material. As the current increases beyond a limit, the wire in the electric fuse melts and breaks off. The fuse is then said to have blown off. The circuit is broken and current stops flowing through it. Thus, a fuse prevents fires. There are various types of fuses. Some fuses are used only in buildings, while others are used in appliances.
Reasons for Excessive Current
When all the appliances are connected to the same socket, these appliances draw more current, and so the load increases. When the insulation on the wires is torn, two wires carrying current touch each other directly. This causes a spark, which leads to fire. This is termed as a SHORT CIRCUIT. If a fuse is not used, then overloading and short circuits result in fire.
Miniature Circuit Breakers (MCB)
Instead of fuses, MCBs are used nowadays because these are switches that turn off automatically when there is an overload or a short circuit. After solving the problem in the circuit, the switch can be turned back on, and then the current flows as usual.
The Magnetic Effect of Electric Current
When electric current flows through a wire wound around an iron bar, the bar behaves like a magnet.
When electric current flows through a wire wound around an iron bar, the bar behaves like a magnet. This magnet is called an electromagnet. An electromagnet is formed due to the magnetic effect of electric current. This magnetic effect of electric current was discovered by Hans Christian Oersted. Once, while preparing for a lecture, he noticed that there was a deflection in the needle of a magnetic compass kept near a wire that was connected to a battery. This deflection occurred every time the battery was switched on and off. He realised that a magnetic field is created around a current-carrying wire in a circuit. The components required to create an electromagnet are two pieces of insulated copper wire, a nail, a battery containing two cells, a bulb with a holder, and some paper clips made of iron. The bulb is also used for making an electromagnet since it serves as a resistance to the current in the circuit and it prevents the battery from quick discharge.
Construction of an Electromagnet
Application of Electromagnet
Electromagnets are used in medicines, toys, iron industries, and most commonly in the electric bell. Cranes are used for lifting material, separating iron from scrap in industries, and to lift cars. These work on the principle of the electromagnet. Electromagnets are also used in electromagnetic trains called Maglev's.
Construction and Working of an Electric Bell Circuit