Difference between load and resistor
We know that a resistor can be considered as a load. Now the question is, if we increase the resistance according to ohm's law V = IR, the current must fall. Again we say that if the load is increased in the circuit, current consumption gets higher. So the question is, what happens to the circuit current if the load is increased or decreased?
Updated: I have updated the answer.
Understanding the Difference Between Load and Resistor: Implications on Circuit Current
Let’s start with the basics; which I hope you’ve paid attention to in your electrical engineering class.
Introduction:
In electronics, two of the fundamental concepts are "load" and "resistor."
To understand these, one must comprehend the rudimentary principles of Ohm's Law, which states that the voltage across an electronic device is equal to the current flowing through it times the resistance of the device (V = I*R).
In this context, we will demystify the concepts of load and resistor and how they affect the current in a circuit.
Resistor:
A resistor is a two-terminal passive electronic component designed to implement a specific amount of resistance to the flow of electric current.
It follows Ohm's Law, where an increase in resistance results in a decrease in current when the voltage is kept constant. This phenomenon happens because resistance is inversely proportional to the current.
Therefore, when resistance rises, it restricts the flow of electric charges (current) through the circuit, assuming the applied voltage is unchanged.
Load:
On the other hand, the term 'load' in an electrical circuit refers to any device or component connected to the circuit that consumes electrical power.
It can be any electrical device like a resistor, motor, or lamp, where electrical energy is transformed into another form such as heat, mechanical work, or light.
When the term "increasing the load" is used, it may refer to adding more load devices to the circuit, not increasing the resistance of a single load.
In a parallel circuit configuration, adding more load (more devices) effectively decreases the total resistance and increases the total current drawn from the source, provided the source voltage remains constant.
Load versus Resistor:
While a resistor can be a load, not all loads are resistors.
For example, loads such as motors and inductors not only have resistance but also exhibit inductance.
Similarly, capacitors have capacitance along with some resistance. These components react differently to AC signals due to these additional properties.
However, to address the initial question - when we increase the resistance of a single load in a circuit, according to Ohm's law, the current does indeed decrease, provided the voltage remains constant.
On the other hand, when we say "increasing the load" in the sense of adding more devices (in parallel configuration), we effectively decrease the total resistance seen by the power source.
This reduction in overall resistance results in a higher current being drawn from the source, given that the source voltage remains constant.
Conversely, if we were to add more devices in a series configuration, this would increase the total resistance, thus decreasing the current flow.
Conclusion:
In summary, the effect on circuit current depends largely on how the load is increased or decreased - whether by altering the resistance of a single component or by adding or removing components.
In addition, the configuration of the circuit - series or parallel - plays a crucial role. The key to understanding these changes lies in a thorough understanding of Ohm's Law and the difference between a load and a resistor.
Replies
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aj_ondutyFirstly you have to consider the fact that the Ohm's law graph is not a straight line when we apply practically.
Secondly, you have to understand the fact that the load what we are discussing here is not always the resistance, the load may be capacitive or inductive, or even all the three. So, we cannot relate it with Ohm's law. To sum up, when the load increases, there is a voltage drop which leads to the increase in current, since power=volt*current*power factor. -
aj_ondutyOhm's law is intended to define the resistance provided by the conductor as the ratio of the voltage applied to the current which flows through the conductor.
But I want more experts to talk about it here. Please do. I hope Voltaire would be watching this thread.
@sayandev, nice question! 👍 -
sushant005@ Aj_onduty: Very nice explanation.
"load is always not resistance."
The above point is very clear to distinguish the load and the resistance. -
sayandevThanks for the explanation. But the thing is that I know that a load can be resistive,inductive,capacitive or a mixing of these. My question is on the fact of change in current in the circuit when we increase load and when we increase impedence in the circuit.
@aj_onduty On the basis of your reply, I am asking you that is there any difference b/w impedence of the conductor and load ??
And please anyone explain me. I am still confused ??? -
sayandev"We know that a resistor can be considered as a load. Now the question is, if we increase the resistance according to ohm's law V = IR, the current must fall. Again we say that if the load is increased in the circuit, current consumption gets higher. So the question is, what happens to the circuit current if the load is increased or decreased??"
please answer to this ... I am really confused. -
sreeram perithe thing is, "lLOAD IS NOT A RESISTOR" resistor a mere representation of a load... consider a practiacal xample of generator, in GENERATOR to generate electricity required to rotate all d fans in a function hall... now here OUTput of generator is electricity,which needs to be increased if number of fans to be rotated increases,here LOAD(fans) draw curent from generator,as load (no. of fans)increases,d generator needs t generate more n more eletricity to meet its demand... hence LOAD and CURRENT are directly proportionaL.. think practically
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aj_ondutyHave you heard of a potential drop?
When we connect a load to the terminals of a generator, what happens is that there is a potential drop across the load. To be in layman's terms, the generator gives and the load consumes. It has to consume the same amount of what the generator is giving.
Suppose we have two resistive loads for instance, R1 and R2 in series. The load should be equal to the total resistance R-
That is,
R=R1+R2------------------(1)
But we know V=IR.
Therefore,
R=V/I---------------------(2)
Similarly,
R1=V1/I1-----------------(3)
R2=V2/I2-----------------(4)
Put (2),(3),(4) in (1),
V/I=V1/I1+V2/I2
But I1=I2=I(Since the connection is in series)
Therefore, we get V=V1+V2.----------(5)(V1 and V2 are the voltage drops across the loads)
That means the whole voltage applied to the system is equal to the sum of the potential drops across the loads. A potential drop is basically equal to a battery connected upside down into the system.According to Kirchhoff's voltage law,the algebraic sum of the voltages in a circuit is zero. This is what I meant by proving the above equation number (5), which can be also said as-
V-V1-V2=0
So, when you go on connecting loads, the work as batteries. They pull more and more current into themselves and thus, during the addition of a load, the current increases. -
sayandevNow suppose I double the load. then?? I think then the potential drop across the load must double, if the circuit current remains constant. But if we keep the voltage source constant, then the current must decrease... Is it so?? which case happens???
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aj_ondutyI saw this doubt right now, I am logged in through my mobile. As my phone does not permit moe than 512characters, i cannot type the answer.I will post the answer tomorrow at 10am! Thanks for asking!
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aj_ondutyHi,
First, consider the fact that in a power system, the voltage cannot be changed.
Let me explain what happens in the power system. When there is no load in the system, the system does run, the power source(generator) supplies for the losses which are present in a power system.
You know the formula of power, for those who don't, P=VIcos(phi). Lets not consider about the cos phi part, as we are interested to know about the V and I in here.
So, the current value will be minimal when there is no load. Now, when you input any load into the system, you are putting in something which is power hungry, which presses your generator to input more power. So, the power in the system increases. That is, P increases. When P increases, V and I must also increase. But V cannot increased, as was mentioned before. So, I should be increased. Thus, when every unit of load is added, the current value increases. This never means that Ohm's law is not followed. The law is followed. but what happens is that the current decrease due to it does not match with the current increase due to increase in power.
Sorry for confusing you in the above posts. Thank you for asking. Please ask more questions. Experts, please comment. -
mehaque87when we increase load or when we increase impedence in the circuit for a particular voltage source as a i/p current will decrease .
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nsiva007Load by what yo ask is the current intake...a heavy load draws more current and less resistance for that matter... while a lighter load means less current drawn and more resistance...!
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sayandevThanks ajit.... then the question is that how everytime is the KVL (kirchoff's voltage law) maintained in the circuit??
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aj_ondutyI believe that all the laws defining the relation of current and voltage with each other or with something else or itself, like the KVL, KCL, Ohm's law follow one basic assumption, the power applied in the circuit is kept constant. Hope I am clear. Hope I am correct. Correct me if I am wrong, Thank you.
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sayandevGot it...😛.. Now its clear.....
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HIMAYUN KHAN 1560712
i am still confused...what is the difference between load and resistance??
and what is resistance....is it positively charge or negatively charged substance?
note: if we dont follow ohm"s law in transmission power. then what is ohms law and why its so famous....
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Ramani Aswath
Ohm’s Law applies. Use impedance instead of resistance.
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Kaustubh Katdare
#-Link-Snipped-# - In electric / electronic circuits; a load is anything that draws current from the circuit. Typically, the household appliances are considered as 'load'; and it's still a 'resistance'.Â
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