“Electrical Resistance is a property of substance which opposes the flow of Electric Current”
Welcome to the world of physics where physics is everywhere.
Well, We all know that in today’s world electricity is the most desired form of energy for our materialistic life. In the term electricity, the thing that flows is current.
To flow, this electric current needs a medium. We call this medium electrical conductor. These electrical conductors are mostly made of metals.
Why do we use mostly metals to make electrical current flow? Why nonmetals are not used? Well, its answer is simple. Metals are good conductors of electricity while nonmetals are not. The nonmetals are a bad conductor or insulator of electricity.
How do we get the idea that few specific matters are good conductors while few are not? Well, we get this idea from their atomic structure. Most free electrons better are the conductor.
What makes these Insulators or the bad conductor a bad conductor of electricity? Well, it is its resistance that makes them fall into the category of an Insulator.
As per the definition, Electrical Resistance is a property of a substance that opposes the flow of electrical current. According to this property, we can classify the matters as conductor, semiconductor, and Insulator.
How Electrical Resistance is connected to other fields of life.
If we talk about resistance it is not limited to electrical energy. Every aspect of life and science has a form of resistance in it.
Resistance and Protests
In the field of humanity, resistance arises when a group of people start to oppose a particular ideology. This is also a kind of resistance, but widely known as protest. Protests are also of both types i.e. positive and negative like resistance.
For better clarity, resistance is not always harmful. If there is no resistance there will be no control over current. Similarly, if there is no protest against a false ideology, it will overcome the entire human race.
Resistance and Friction in Mechanical Bodies
We all know friction is one of the most important physical attributes to sustain life on earth. Resistance is very much similar to friction.
Friction opposes any kind motion as resistance opposes the flow of current. So we can say, friction and resistance both are the same quality of quantity working in two different fields.
If we talk about the positive and negative factors of both they’ll be as follows-
Positive- Like resistance supports the electrical circuits to withhold the current similarly friction withhold the objects in their contacts.
Negative- Like resistance becomes a big reason in dissipation of energy, similarly friction is the biggest reason of mechanical damage.
Resistance And Reluctance in Magnetic field
Reluctance works in magnetic fields like resistance works in electrical fields. Magnetic fields have flux as electric fields have current. Reluctance opposes the flow of flux in the magnetic field like resistance opposes the flow of current in the electric field.
Factors Affecting the Electrical Resistance
We must have studied the equation for the resistance mentioned below.
Where R = the Value of Electrical Resistance
ρ = The resistivity of the conductor material
l = The length of the conductor
a = the cross-sectional area of the conductor
From this equation, we can clearly see that resistance is directly dependent on the three attributes of the conductor material. One is its resistivity which is dependent on the material. 2nd is its length and the third is its cross-sectional area.
Resistivity and the length are directly proportional to the resistance while the cross-sectional area is inversely proportional.
How type of materials affect Resistance.
Before going to start anything related to this topic, I would like to introduce you to the definition of Resistivity.
“Resistivity or the specific resistance is the value of resistance of unit length conductor or simply a specimen of the conductor.” it is measured in ohm-cm.
Every material on the Earth has its own resistance and we all know it’s because of its atomic structure.
Few materials have better conductivity and low resistivity. Few have lower conductivity and higher resistivity.
For Example – SIlver has a resistivity of 1.59 x 10^-8 ohm-m, copper has 1.68 x 10^-8, and Aluminium has 2.65 x 10^-8.
From this we can say, a conductor made of Aluminium will have more resistance for the same size of a conductor made of Silver.
So, we can easily say that the resistance of the conductor is directly dependent on the material it is made of.
How Length is affecting the Resistance?
From the formula above, it is clear that the resistance of the conductor is directly proportional to its length. Means longer the conductor, higher will be the resistance. Shorter the conductor, the lower the resistance will be.
It is because the electrons have to travel a longer path.
That is why in house wiring the main wire which is going to the switchboards are taken a high cross-sectional area wire to compensate its resistance due to the longer length.
How Cross sectional Area Affects the Resistance?
From the formula above, it is clear that the resistance of the conductor is inversely proportional to the cross-sectional area of the conductor. Means thicker the conductor, lower will be the resistance. Thinner the wire, higher the resistance.
It is because the electrons have a larger area to flow.
Law that Derived the Resistance
If you have any interest in physics then you must know a name and that is George Simon Ohm. He was a physicist from Germany. He gave a very famous law named after his name Ohm’s Law.
What Does Ohm’s Law Say?
According to Ohm’s Law “At constant temperature and pressure, the current flowing through a circuit is directly proportional to the voltage applied to the circuit.”
Mathematical representation will be as follows.
V ∝ I
Here V = the Voltage applied to the circuit
I = The Current flowing through the circuit.
Now we need to replace this proportional symbol with constant to make this representation an equation.
But, how to find the constant quantity in an electrical circuit? Well, think deeper, voltage applied always fluctuates so it can’t be a constant quantity. Current is directly proportional to the voltage applied so it also can’t be a constant.
Now, think more deeper, what are fixed in electrical circuits? Let me remind you, there are 3 things fixed, which can’t be varied in an operational electrical circuit.
- Type of Material used for conductor
- Conductor Length
- Conductor cross sectional area
Type of Material Used for Conductor
If we had used copper as conductor material, we couldn’t replace it during the operational period. So, it is no doubt a fixed thing.
It is the length of the conductor connected from the source to the load in that electrical circuit. This length is predefined, and can’t be changed. So, it is also a constant quantity.
Conductor’s Cross Sectional Area
If we had used a certain size of the conductor, it is not good to replace it with a different sized conductor. So, without any doubt, it is also a fixed object.
From these three fixed objects, we come to the conclusion that a quantity affected by these objects will always be constant. And that quantity is the overall Electrical Resistance of the circuit.
So, now, we can rewrite the above mathematical representation as below
V = I R
Here, R is a constant quantity here. So we can multiply resistance to get the actual equation.
From all these above elaborations, it is clear that Ohm’s Law is the law which derives the resistance of an electrical circuit.
Due to the contributions of Mr. George Simon Ohm in this law, the scientists named it in his honor and made him immortal in the books of Science.
This law is the base of the calculation of electrical resistance. So, scientists made the unit of resistance after his name.
We have studied electrical resistance which is a very important quantity in the field of electrical engineering. Resistance is the property of a substance which opposes the flow of current in an electrical circuit.
It controls the electrical current in a circuit. By controlling means, we can divert the path of the current by using a resistor and can manipulate its value as well.
As we studied resistance is an important quantity, it means it not only has the positive angle of controlling but it also has negative sides. It must be in the controlled order else it could create a big mess and energy loss.
That’s it for today, we will meet again with new and more knowledgeable content. So, tata, bye-bye.
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