Resistance: Definition, Symbol,Working Principle, Use of It
When we apply electric potential across any conductor, bulb or heater coil then electric current flows through it but when electric current starts flowing through the conductor the conductor material opposes the flow of electric current. The reason why any conductor opposes flow of electric current is known as resistance. Because of it when current flows through any conductor it produces some heat.Every material has its own nature toward electric potential. On the basis of their behaviour in electrical material they are divided into three parts.
Conductors( this type of materials have low resistance. It is used for making wire and coils.)
Semiconductor (this type of materials have resistance more than conductor but less than Insulators.)
Insulators (this type of materials have high resistance. Such type of materials are not flow of electric current through itself. )
In this article we know more about resistance and resistor
Resistance:- when electric potential is applied across any type of conductor electrons start to flow through it but in this process electrons collide with each other and atoms of material which oppose the flow of electric current through it this type of opposition is known as resistance. Because of resistance energy is emitted in the form of heat. This is the reason why any material that maintains the flow of electric current becomes hot.
Unit:- Unit of resistance is ohm(Ω).
Symbol and diagram:- symbol and diagram of resistance is given in figure: -
Formula:- The formula for resistance is given below by Ohm's law
R= V/I ohm.
Function or working principle of Resistor -
Function of a Resistor:
Limits Current: By adding a resistor in a circuit we can control or limit the current in that circuit because when we add a resistor in an electric circuit in series it increases the total resistance of the circuit. That's why the total current in the circuit becomes low.
Divides Voltage: We can use a resistor as a voltage divider. When we connect a resistor in a circuit in series sequence it works like a voltage divider. Because some voltage drop occurs across it.
Protected Components: By using it we can limit or control current in a circuit so we can protect some sensible components that do not permit flow of excess current through it. Many electrical and electronics circuits we use for this purpose.
Working Principle of a Resistor:
Resistor : A resistor has a specific amount of resistance, measured in ohms (Ω). This resistance opposes the flow of electric current.
Heat Dissipation: As current passes through the resistor, some of the electrical energy is dissipated in the form of heat.
6.Type of resistor :- There are many type of resistor are available in this time:-
a).Fixed Resistors: This type of resistor have fix value of resistance
Carbon Film Resistors: it is made from a carbon film, commonly used in general circuits.
Metal Film Resistors: This type of resistor is made from a metal film, known for its accuracy and stability.
Wire-Wound Resistors: It is made by high resistivity conductor wire winding around a core, used for high-power applications.
b).Variable Resistors: in this type of resistor we can adjust the value of resistance. there are few such type of resistor are given below:
Potentiometers: It is a resistor which has three terminals,two are fixed and one is moveable, used to adjust voltage in a circuit.
It is mainly used in:
Volume Control: In audio equipment to adjust sound levels.
Dimmers: To control light brightness.
Rheostats:This type of resistor is used in labs and some industries.it is used to control current flow.
c).Special Resistors:This type of resistor used for special purposes:
Thermistors: This type of resistor’s resistance changes with temperature; used for temperature sensing.This type of resistor used in fridge, Air conditioner and other temperature sensing gadgets.
LDRs (Light Dependent Resistors): As the name of the resistor tells us. In such a type of resistor's resistance changes with light intensity; used in light-sensing applications.This type of resistor used in street lighting systems.
d).Surface Mount Resistors: With evolution of technology electronic technology also evolves. So the small resistors used on printed circuit boards (PCBs).Because with the evolution of a simplified circuit, use less power consumption and high quality gadgets.
7.Common material used in Resistor:-
There are many types of resistors used today.So different types of resistor have different material composition.
Carbon composition resistor: It is used in low power circuits. It is made of carbon dust and graphite paste. Such type of resistor's resistance value calculated from colour band reading.
Cermet resistor or film resistor:This type of resistor is used for low power circuits. It is made from conductive metal oxide paste.
Wire wound resistor: This type of resistor is used for high power circuits. And it is made of nichrome wire wound around a core which is made from a ceramic or fibreglass.
8.Resistors in different types of circuit :- Resistors are used in different circuits like parallel Resistor circuit, series resistor circuit, mix (series and parallel both)resistor circuit.
In series circuit resistors are connected with other resistors one after another. In this type of circuit, the total resistance of the whole circuit is more than each resistor. And in this type of circuit current is the same in every resistor. But voltage drop across each resistor may be different. If two resistors are connected in a series circuit then and the resistance of each resistor is different then voltage drop of across each resistor will be different.
(Parallel resistor circuit) In this type of circuit the resistors are connected parallel with each other and the total resistance of the circuit is less than every resistor which is used in the circuit. The voltage drop across each resistor will be the same. But electric current flow through in every resistor will be different; it depends on the resistance of the circuit.
( parallel and series )mix resistor circuit: this type of resistor circuit has both types of resistor circuit. If we want to know the total resistance In this type of resistor circuit we need to solve the first parallel circuit after adding the value of resistance of each type of resistor which is in series. We see this type of circuit in mainly complex circuits.
9.Resistor’s resistance checking circuit and tool:-
If we want to check The resistor's resistance then we need an instrument named multimetre. First we have to take that resistor and after it connect the both nobs of multimetre to the resistor terminals and after it we get the resistance of it in ohm(Ω),k(Ω),M(Ω) on the display of multimetre.
Wheatstone bridge: - it is a circuit which is used for measuring resistor resistance. It is mainly used for low resistor's resistance measurement.
10.Power rating and tolerance of Resistor :-
Power rating of resistor: Power rating of Resistor is defined as the maximum power which can be borne by a resistor without burnout is known as power rating of resistor.
P= V×I watt.
Tolerance of resistor: The tolerance of resistor is defined as the divergence from the nominal value of resistance. If we want to know about divergence of nominal resistance value then we need to see forth band of resistor colour band if this is
Golden then tolerance is 5℅
Silver then tolerance is 10℅
And no forth colour band then tolerance is 20 ℅
11.Use of resistors in daily life:- In our daily life we see resistors in different types of circuits like charging circuit, current controller, regulator, television circuit,mobile /computer/laptops and other electronic circuits.
12.Difference between Resistor and Resistance:- Resistor is a component which is used in different types of circuit and the resistance is the property of materials by which it opposes the flow of electric current through itself.
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