Hi Mr Electro family!! This is an educational website for electrical stream ( Electrical engineering, Diploma student and PreDiploma students) . This is mainly focused for those students who are waiting for Government jobs like LokSewa Aayog PSC, NEA, CANN NTC for level 3, level 4, level 5 and level 7 and also private jobs.

Thursday, October 20, 2022

Resistor symbol || What is resistor ?

The electrical or electronic device which absorb or dissipate energy in different form are called passive components. These component doesn't have amplifying property so that these components won't increase strength or add power to the incoming signal. The example of these components are resistor, capacitor, inductor etc. Let's discuss about "Resistor symbol and What is resistor ? " Resistor is an passive component which will oppose the motion of electron or electric current in a circuit. In any electrical (low voltage) as well as electronic, it is widely used for designing most of the circuit. In designing electrical circuit, resistor symbol need to be added.

Since current is the flow of free electron and resistance is the opposition of free electron so we can said that the opposition of current is called resistance. For that opposition of movement of free electron, the atoms and molecules of that material will obstruct the free electro. In an electrical circuit, some material offer less amount of opposition of current flow (like cupper, silver, aluminum ) and in other hand, some material provide high amount of opposition of current flow (like glass, rubber, mica).

Resistor symbol 

Resistor symbol is given below:-

Resistor symbol || What is resistor ?


Resistor symbol || What is resistor ?

These are resistor symbol or resistance symbol and we can use any of them in circuit drawing or designing. We already know that the material which oppose the movement of electro is called resistor and this property is known as resistance. Generally, it is denoted by 'R' and measured in terms of ohm ( Ω ). 

Role of resistor

As we know resistor oppose or block the flow of current so there is power loss in the form of heat. Due to these property, resistor can be used in electrical equipment as a heating element. It is used in irons, electrical heater, filaments lamps. Also it is used in limiting current in the circuit as it oppose the flow of free electron or current in the circuit. For same voltage source, current will decrease with increase in voltage in that way it will used to reduce current in a circuit. For that variable resistor is needed so that, resistance of resistor can be changed to change current in the circuit like rheostat (variable resistor), fan speed regulator etc. It is also used in changing or dividing the voltage level in a circuit. For same current level in a circuit, voltage can be divided by using resistor.

Resistance of resistor

Resistance of a conductor is directly proportional to the length of conductor and inversely proportional to the cross-sectional area of that conductor. So the resistance of a conductor is given by,
    R = ρl / A
Where, R = resistance of the conductor ( ohm or Ω )
             ρ = resistivity of the conductor ( Ωm )
             l = length of the conductor ( m )
             A = Cross-sectional area of conductor ( m² )
Here, resistivity of the material is defined as the resistance of that material at unit length and unit cross-sectional area of that conductor. It depends on the material of conductor and we can choose the resistor material according to it as our requirement. For high resistance, we can use mica, glass which has higher resistivity and for low resistance, we can use silver, cupper which has less resistivity. The reciprocal of resistivity is called conductivity which is represented by G and given by,
    G = 1 / R
Its unit is mho or siemens.

Resistance with temperature

Resistance of a conductor varies on change in temperature. Resistance is directly proportional to temperature i.e. resistance increase with increase in temperature and decrease with decrease in temperature. For that we have a relation:-
R₂ = R₁ [ 1 + α (T₂ - T₁) ]
where, T₂ = final temperature
            T₁ = initial temperature
            α = Temperature coefficient of resistance at T₁
            R₁ = Resistance at T₁
            R₂ = Resistance at T₂
This formula or concept is only applicable in conductor. In semiconductor and insulator, resistance decrease with increase in temperature.

Ohm's law

From ohm's law, we can relate the relation between voltage, current and resistance in a circuit. Let us consider, a DC circuit has voltage source of 'V' voltage, resistance 'R' and current flowing in the circuit is 'I' respectively. Then, their relation can be written as,
    V = IR
This is called ohm's law which means the voltage of any circuit will be directly proportional to the current in that circuit at constant other condition (same material. same environment) i.e. V α I
The value of 'R' (resistance) depends on type of materials, shape & size, and environmental condition (like temperature).  If a wire has 1 Ω resistance in a circuit which has 1 V voltage then 1 A current will flow in that circuit.

Types of Resistor

1. Carbon resistor
2. Film resistor
3. Fusible resistor
4. Variable resistor

Resistance connection

In an electrical circuit, there are different types of connection which is complex but it can be simplify it by two connection. They are as follows:-

1. series connection of resistor

In series connection, there are more than one resistor in series which will increase the resistance of circuit. All resistor's resistance need to be summed to get the whole circuit resistance. For example, a circuit has series resistance of R1, R2, R3, R4 and so on. For whole circuit resistance is given by,
     R = R1 + R2 + R3 + R4 + ......

2. Parallel connection of resistor

In parallel connection, there are more than one resistor in parallel which will decrease the resistance of the circuit. The reciprocal of resistor's resistance need to be summed to get the reciprocal of whole circuit resistance. For example, a circuit has parallel resistance of R1, R2, R3, R4 and so on. For the whole circuit resistance is given by,
    1 / R =  1 / R1 + 1 /  R2 + 1 / R3 + 1 / R4 + ......

No comments:

Post a Comment

----Please share your opinion with us-----