Hey friends, welcome to the new post on All About Electronics and today we will see Ohm's law in the electrical circuit.
So Ohm's law is very simple algebraic relationship between the voltage, current and the resistor in the circuit. So, let us say we have one voltage source which is connected to a one resistor R.So, because of that the current will flow through this resistor R. So, according to the Ohm's law at constant temperature the electrical current flowing through a fixed linear resistor is directly proportional to the voltage applied across it and it is inversely proportional to the resistance.
The current which is flowing through this resistor R is directly proportional to the voltage applied across it and it is inversely proportional to the resistance of this resistor. So, now let's understand this Ohm's law by taking a water tank analogy. So, let's say we have one water tank and at the bottom of the tank we have connected one hose pipe. Soin this analogy the water in the water tank can be represented as a charge in the electrical circuits.
While the level of the water in the tank or a water pressure represents the voltage in the electrical circuit. The diameter of this hose pipe represents the resistance in the circuit and the flow of water through this hose pipe represents the current in the electrical circuit. So, now let's take up one example. Here, we have a two water tanks which contains an equal amount of water in the both the tanks. But the both the tanks have a different diameter of hose pipe.
So, definitely the tank which has a larger diameter hose pipe will have a more flow of water. In the second case, where the diameter of the hose pipe is small, the flow of water will be less. Because the water will observe more amount of resistance through this lower diameter hose pipe. While when it flows through a larger diameter hose pipe, it feels less amount of resistance.
Let's correlate it with the electrical circuit. Let us say that we have a two electrical circuit which has a same voltage sources but the value of resistance in the both the circuit is different. In one case one case it is R1 and in second because it is R2. And So according to the Ohm's law, the current flowing in the first circuit can be given as V divide by R1. In the second circuit, it can be given as I 2 is equal to V divide by R2. Now here, the resistance R2 is less than R 1, so the more current will flow through this second circuit as the value of resistance is less.
But in the first circuit, as the value of resistance R1 is more, So less amount of current will flow. So for both the circuits I 2 will be greater than I1. Now let us take second example in which we have a two water tanks with the same diameter of hose pipe but in the both the tanks the amount of water level is different. In the first tank we have a less amount of water, so because of that pressure exerted at the bottom of this hose pipe will be less.
Because of the less pressure, the flow of water will be less. While in the second case, as it contains more amount of water the pressure exerted at the bottom of the hose pipe will be more. Because of the more pressure the flow of water will be more through this pipe. So now let us correlate it with the electrical circuit. So, let us say we have our two electrical circuits with a different voltage sources. But both the circuit contains a same amount of resistance, that is R.
The current flowing through the First Circuit I1 can be given as V 1 divide by R. While in the Second Circuit, it can be even by I2 is equal to V2 /R. Now here the voltage source V 2 is greater than V 1, so the more amount of current will flow through the second circuit. So we can say that for both the circuits if V2 is greater than V 1 then I 2 will be greater than I1. So through this both both the examples, we have seen that if we keep one parameter constant.
Let's say if we keep voltage constant and we change the value of resistance, or if we increase the value of resistor R then the current will reduce in the circuit, or if we keep the resistance R constant and if we increase or decrease the value of voltage in the circuit and accordingly the current will increase or decrease proportionally. So, now let's take a examples based on the Ohm's law.
In the first circuit we have a one voltage source with a 5 volt which is connected to a 10 ohm resistor. So we need to find what is the current that is flowing through this 10 ohm resistor. So the current I can be given as V divide by R. so here the voltage is 5 volt and the resistance is a 10 ohm. So the current flowing through this circuit can be given as a 0.5 ampere, now in the second circuit if you see we have one 5 volt voltage source which is connected to a unknown resistor R.
And the current that is flowing through this circuit is given as a 2 ampere. So we need to find , what is the value of this resistance R. So we know that according to the Ohm's law, I is equal to V divide by R.So we can write R is equal to V divide by R. Now here we know the voltage that is a 5 volt,and the current that is flowing through that circuit is a 2 ampere. From this the value of unknown the resistance will be the 2.5 ohm.
Basically this Ohm's law is a relationship between the voltage, current and resistor. so if you know any of the two quantities you can find the third one.So let's say you know the current and the resistance in the circuit then voltage can be defined as V is equal to I*R. Or if we know the voltage and current in the circuit then the resistance R can be given as V divide by I that is V divide by i .
Likewise, current I can be given as V divide by R. so in the Ohm's law if we know any of the two quantities we can find the third one. now so in the last video we had seen, what is power in the electrical circuits. And it is given by relationship P is equal to V *I .so according to the Ohm's law we know that the current I can be given as V divide by R Now let's put this into this equation so we'll get V*(V/R),that is a V^2/R. so power can also be defined by V^2/R. now we know that what voltage can also be written as I *R, according to the Ohm's law.
So this power P that is V into I can also be written as(I*R)*I, that is a I^2*R. so power can be defined as either product of voltage into current or V^2/R or I^2*R. so in this way we get a relationship between the power, voltage, current and the resistance in the circuit. So let's see this pie chart which shows all the possible relationship between the voltage, current, power and resistor.
Here if we know any of the two parameters in the circuit let's say if we know current and power in the circuit then we can find the remaining two parameters in the circuit . so if you know current and power when the voltage can be defined as a P divide by I. Likewise, the resistance R can be defined as a P divide by I square. so in this way if we know any of the two parameters, we can find the remaining two .
Let's say if we know power and resistor in the circuit then we can find the current by square root P divide by R and the voltage that is given by square root P into R. so in this way if you know any of the two quantities we can find the other two. so let's take a example based on this relationship. We have one 10 volt voltage source which is connected to a unknown resistor R .And the current is given that that which is flowing through the circuit is a 2 ampere . So, we need to find the value of this resistor and the power dissipated across this resistor. so first of all, let's find the value of this resistance. so according to the Ohm's law R is given by V /I .so here voltage is given that is 10 V and the current that is flowing to the circuit is a 2 A.
From that we find that the value of resistance R is a 5 ohm. Now the power P we had seen that it can be defined as V*I. So, here we know the voltage is a 10 volt and the current is a 2 ampere. The power that is dissipated across the resistor will be 20 W. Now let us take one more example, here we have a unknown voltage source V which is connected to a 10 ohm resistor. And the current flowing through the circuit is given, I is equal to 1 A . So, we need to find the voltage, this unknown voltage and the power dissipated across this 10 ohm resistor. So, first of all, let's find the voltage V which is given by I * R.
Here we know the I is 1 ampere and the value of resistor R is a 10 ohm. So the voltage in the circuit will be the 10 volt. And the unknown voltage source has a voltage of 10 volt. Now the power P can be given by I^2*R, that we already have seen. So here current is 1 ampere that is a 1 square into, R that is a 10 ohm so we get a 10 W.
So, the power dissipated across the resistor will be 10 W. So, using this Ohm's law we can find the voltage, power current and resistor in an electrical circuit, if we know any of the two parameters in the electrical circuit.
I hope you understood what is Ohm's Law in the electrical circuit and using this how you can find the four different parameters in the electrical circuit.
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