Ohm’s Law-Calculator, Formula, Definition, Equation, Wheel

Georg Simon Ohm, a German physicist, and mathematician gave Ohm’s law to the world. This law proved to be very important in physics, particularly for the discovery and invention of electrochemistry. It helps study electrical circuits, resistive circuits, reactive circuits, hydraulic analogy, heat conductivity, etc. Ohm published his law in the research paper “The Galvanic Circuit Investigated Mathematically.” the report was publicized in 1827. The materials obeying this law were called Ohmic or Linear. 

Ohm’s Law

Ohm’s law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points at a particular temperature. Here, Resistance is introduced as the constant of proportionality. Resistance is the opposition to the current in the circuit. Ohm’s law expresses the alliance between voltage, current, and Resistance. 

Ohm states this law in a very simple form of the equation. This law makes it easy to understand electric circuits. According to Ohm’s law, the relation between the current through a circuit and the voltage across that circuit are given as follows.

      I ∝ V

          V 
I =   —
          R

Where I is the current flowing through the circuit, V is the voltage across the circuit, and R is the resistance provided by the conductor to the current. Current is the flow of electrons or electricity in an electric circuit whereas a voltage is a potential difference in charge between two points of a conductor or circuit. Ohm helps us derive the formulae for voltage, current, and resistance from his law. The current through the circuit can be measured using the following formula

       V
I=  ―
       R

The Voltage across the circuit can be measured using the following formula        

V=IR

The Resistance in the circuit can be measured using the following formula 

          V
R =  ―
          I

Ohm’s law Unit

Ohm’s law Unit According to Ohm’s law, the unit of current, voltage, and resistance are as follows:

  1. The unit of electric current flowing through the circuit is given by Ampere. A flow of one Ampere current is produced in resistance of 1 ohm by the voltage of one voltage. Ampere is indicated by ‘A.’
  2. The unit of voltage across the circuit is Volt. One Volt is the potential difference that would carry one Ampere of current through a resistance of one ohm. Volt is indicated by ‘V.’
  3. The unit of resistance opposing the current is Ohm. One ohm is the resistance produced by the flow of the current of one Ampere through a potential difference of one volt. It is indicated by ‘’. This is a Greek uppercase letter called Omega. Also, it is referred to as Ohm when said about resistance.
                     1 Volt
1  Ohm =    ―――
                         1 Ampere

Formula Chart For Ohm’s Law

Ohm’s LawVoltage (V)Current (I)Resistance (R)Power (P)
Current & ResistanceV= IRP= I2 R
Current & Power P
V= ―
I
P
R = ―
I2
Voltage & Current V
R= —
I
P= VI
Voltage & Resistance V
I= ―
R
V 2
p= ―
R
Voltage & Power P
I= ―
V
V 2
R= ―
P
Power & ResistanceV= √PRI= √(P/R)

Also Read: Ohms Law Cartoon-Volt, Amp, Ohms Explained


Ohm’s Law for Combination of Resistors in Circuits

There are two ways to a connection of resistors. The resistors can be joined in series or parallel or series and parallel both.

ACCUMULATION OF RESISTORS IN SERIES

In a series circuit, the resistors are connected beside each other, i.e. they are joined in a line. No other element of the circuit is connected between any two circuits. Only one end of a resistor is connected to the end of the additional resistor. ‘N’ number of resistors can be connected. In the series connection, the current flowing through all the resistors is the same, while the voltage across each resistor is different. The series combination of resistors is shown below.

Let us assume that ‘I’ is the current flowing through these resistors. The resistance of the first resistor is “, the second resistor is” and so on. Let the voltage across the first resistor be “, for the second resistor be ‘.

Then by Ohm’s law, the voltage across each resistor is given as:

V1= I × R1
V1=I × R2
V3=I × R3, so on.
The total equivalent voltage across the circuit is V equivalent=  V11+ V2+V3+ ….+ Vn
IR Equivalent = IR1+ IR2+ IR3+……. + IRn
Therefore, the total amount of resistance applied by the circuit is given by
R Equivalent=R1+ R2+ R3+……. + Rn.

ACCUMULATION OF RESISTORS IN PARALLEL

In a parallel circuit, the resistances can be joined parallel to each other i.e. they are attached one below the other. Both the ends of a resistor are connected to both the ends of the other resistor. In a circuit, a connection of ‘N’ number of resistors can be done parallel to each other.

In the parallel connection, the voltage across one resistor is the same as the voltage across the different resistors connected in that circuit while the current flowing through each resistor varies according to each resistor. The parallel combination of resistors is demonstrated below

Let us consider that the voltage across these resistors be ‘V’. The resistance of the first resistor be R1, the second resistor be R2and so on. Let the current flowing through the first resistor be ‘I1’, through the second resistor be ‘I2‘.

Then by Ohm’s law, the current through each resistor is given as:

          V
I1=   ―
          R1



          V
I2=   ―
          R2




          V
I3=   ―
          R3


The total equivalent current through the circuit is I equivalent= I1+ I2+I3+ ….+ In  

So by substituting, we get  V/R_equivalent =  V/R1 +   V/R22+  V/R3 + ….. +V/Rn .

Therefore, the total amount of resistance applied by the circuit is given by

1/R equivalent =  1/R1 +   1/R2 +  1/R3 + …… +1/Rn 

Ohm’s Law Equation

As Ohm’s law states, the current is directly proportional to the voltage with resistance as the constant of proportionality. We get

Voltage = Current x Resistance 
V=I ×R

The current opposes the flow of current which is said to be Resistance. The current is the discharge of electrons. But while flowing through a wire of circuit it has to overcome the resistance given by the wire and flow through the circuit. The equation for Ohm’s law Resistance is given by

          V
R=   ―
          I

Example 1

If the resistance of a circuit is 50through which a current of 3.2 A is flowing, then find the voltage across this circuit.

Solution:

We have to find voltage when we are given the resistance and current in the circuit. So, we will use the voltage formula.

According to Ohm’s law, 

V = IR
V = 3.2 x 50
V = 160 Volts.

So, the voltage obtained across the provided circuit is measured as 160 volts.

Example 2

If the resistance of a circuit is 25through which a current of 6 A is flowing, then find the voltage across this circuit.

Solution:

We have to find voltage when we are given the resistance and current in the circuit. So, we will use the voltage formula.

According to Ohm’s law, 

V = IR
By substituting the given values of resistance and current in the formula, we get
V = 6 x 25
V = 150 Volts.

So, the voltage obtained across the provided circuit is measured as 150 volts.

Example 3

The voltage across a circuit is 6.56 V while the resistance of the same circuit is 1.6 ohms. To how much current is the resistance or opposition applied?

Solution:

We have to find the current in the circuit when the voltage and resistance of the circuit are given to us. So we will use the current and solve this problem.

According to Ohm’s law,

          V
I=   ―
          R
By substituting the given values of voltage and resistance in the formula, we get



          6.56
I =   ―
          1.6

I= 4.1 A

The current flowing through the given circuit is 4.1 A.

Example 4

Find the current in a circuit to which resistance of 9.75 ohms is applied. The voltage across the circuit is 8 V.

Solution:

We have to find the current in the circuit when the voltage and resistance of the circuit are given to us. So we will use the current and solve this problem.

According to Ohm’s law,

          V
I=   ―
          R

By substituting the given values of voltage and resistance in the formula, we get



          8
I =   ―
          9.75

I= 0.82 A

The current flowing through the given circuit is 0.82 A.

Example 5

The current flowing through a circuit is 5 A while the voltage across the circuit is 200 V. What is the resistance applied by the circuit on the flow of current?

Solution:

We have to find the resistance of the circuit when the voltage and current in the circuit are given to us. So, we will use the resistance formula to solve this problem.

According to Ohm’s law,

          V
R=   ―
          I

By substituting the given values of voltage and current in the formula, we get



          200
R =   ―
          5

R=40 Ω

So, the resistance to the current in the given circuit is 40 ohms.

Example 6

The current flowing through a circuit is 4.2 A while the voltage across the circuit is 210 V. What is the resistance applied by the circuit on the flow of current?

Solution:

We have to find the resistance of the circuit when the voltage and current in the circuit are given to us. So, we will use the resistance formula to solve this problem.

According to Ohm’s law,

          V
R=   ―
          I

By substituting the given values of voltage and current in the formula, we get


          210
R =   ―
          4.2

R=50 Ω

So, the resistance to the current in the given circuit is 50 ohms.

Ohm’s Law Equation Triangle

The ohm’s law equation triangle consists of all the terms in Ohm’s law. It includes voltage, current, and resistance. This triangle helps to solve the problems quickly. If the triangle shows the words placed in a horizontal line, then they are in multiplication. When it shows the terms in a vertical line, then they are in the division. The formulae can be guessed just by looking at them.

Ohm’s Law Equation Triangle
Ohm’s Law Equation Triangle

Steps for using the Ohm’s law triangle

Step 1

Note the term that you are trying to find: Current(I), Voltage (V), Resistance (R), or Power (P).

Step 2

Now, note the two terms whose value you are given: Current(I), Voltage (V), Resistance (R), or Power (P).

Step 3

Let’s say that you are given the values of current and resistance and you have to find the voltage of the circuit. That means that I and R are given.

Step 4

If the triangle shows that the terms placed are in horizontal line then they are in multiplication.

Step 5

If the triangle shows that the terms placed are in a vertical line then they are in the division.

Step 6

Now keep your hand on the value you have to find i.e. voltage.

Step 7

Since current and resistance both are visible in a horizontal line, you can say that they both are in multiplication

Step 8

From this, you get the formula of voltage that is voltage is equal to resistance into the current


Ohm’s Law Definition

The direct current or the current flowing through a resistor is directly proportional to the voltage across that resistance and vice versa. This means that when the voltage is increasing with no change in the resistance of the circuit, then the current will also be in increasing order.

I ∝ V

V ∝ I

Explanation:   To measure the current, use the formula:  I = V/R Here, the resistance is kept constant while the voltage is increased by a small amount each time. There is a gradual increase in the current with every increase in the voltage.

VoltageResistanceCurrent
200 volts50 ohms4 amperes
250 volts50 ohms5 amperes
300 volts50 ohmsamperes

The current passing through the resistor is inversely symmetrical to the opposition to the current in that resistor. This means that when the resistance of the circuit is increasing, then the current will be decreasing. The condition for this to happen is that the voltage remains constant.

        1
I  ∝  ―
        R

Explanation: To measure the current, use the formula: I = V/R. Here, the voltage is kept constant and the resistance is increased by a small amount each time. There is a decrease observed in the current as the resistance is increased.

ResistanceVoltageCurrent
20 ohms200 volts10 amperes
40 ohms200 volts5 amperes
50 ohms200 volts4 amperes

The voltage across the resistor of a conductor is directly proportional to the resistance of that resistor. This means that when there is an increase in the voltage with no change in the current flowing, then an increase in the resistance of the circuit is observed.   

V ∝ R

Explanation: To measure the current, use the formula:  R= V/I. Here, the current is kept constant and the voltage is increased by a small amount each time. There is an increase observed in the resistance as the voltage is increased gradually.

VoltageCurrentResistance
200 volts4 amperes50 ohms
240 volts4 amperes60 ohms
280 volts4 amperes70 ohms

Pie Shaped Wheel for Ohm’s Law

The pie-shaped wheel for ohm’s law is used for making problem-solving easy. It is a representation of Ohm’s law with the use of the pie formula. This wheel is a type of formulae chart.

The wheel has been separated into four parts. Each part represents a different term. The parts have three formulae each. The division of the wheel is done in the following parts.

  • Current marked by I
  • Voltage marked by V
  • Resistance marked by R
  • Power marked by P
Ohms Law Pie Chart
Ohms Law Pie Chart

How To Use Ohm’s Law Pie-Shaped Wheel

  • Step 1: Note which term is trying to find: Current (I), Voltage (V), Resistance (R), or Power (P).
  • Step 2: Now, note the two terms whose values you have: Current (I), Voltage (V), Resistance (R), or Power (P).
  • Step 3: Then, Find the part of the wheel that fits all the three terms (a term that you need and the other two that you already have.)
  • Step 4: When you find the related formula, you can solve the problem easily.

NOTE: An important thing that you need to remember is that the units of the terms given and to be found should be compatible i.e. you have to convert milliamperes into ampere, kilovolts into volts, kilohms into ohms, etc.

How To Remember Ohm’s Law Pie-Shaped Wheel

  • Tip 1: When we look at the formula wheel, we see many formulae. But in reality, there are only two main formulae.
  • Tip 2: T the top of the wheel, we can see the formula V = R x I. The other formula is found when we go round the wheel. The 1oth formula i.e. P = V x I is the other one.
  • Tip 3: Now let’s make the other formulae with the help of these two basic formulae.
  • Tip 4: Since, V = R x I. We can substitute for V in P = V x I. We get, P = R X I2 the formula for power in terms of resistance. This is the 11th formula in the wheel.
  • Tip 5: Similarly the other formulae can be made. You don’t have to learn the entire wheel. Just remember the two main formulae.

Ohm’s Law Made Easy to Understand

Electricity is a very hard chapter for everybody so stress if you are having a hard time learning it or understanding it. let’s try to make concepts easy using simple words.

Voltage

  • Voltage can be defined as the stability of charge between two points in simple words.
  • The unit Volt is used to measure voltage.
  • E or V is the symbol given to voltage.

Current

  • Current in simple words can be defined as the number of electrons passing through a point. Another way to express current is amperage.
  • Ampere is used to measure the current.
  • ‘I’ is the symbol used to represent the current.

Resistance

  • Resistance can be simply defined as an opposition to the flow of electrons in a wire.
  • Ohms is used to measuring resistance.
  • R is the symbol used to represent resistance.

Power

  • Power can simply be defined as the transfer of electric energy into another form.
  • Watts is used to scaling power.
  • P is the symbol used to represent power.

An easy way to remember how these terms work together

Let’s consider electricity as tank water that is going through a hose. When the water travels through a hose, a force or pressure is applied to it. Let’s say that this pressure is Voltage. Due to this pressure, the flow of water through the hose can be considered the Current. Every hose has some variations in it. These variations oppose the flow of water, or less water can go through it. We can say that these variations are ResistanceResistance. Now imagine the water sprinkling through a water spray. This water spray is causing the water to spin. We can say that this is Power.

Ohm’s law relates the terms voltage, Current, and ResistanceResistance mathematically, expressed as Voltage is Current into ResistanceResistance.

Using the above denotations, you can write this as V= I x R.

You can also write I = V /R and R= V/I.

Example 1


Let us consider an example to understand this easily. You have a circuit with a 10 volts battery and a resistor that has a resistance of 2 ohms. Now you have to find the value of current through your circuit.
If you put the values given to you in the above equation, then we get a simple equation that looks like: 10 V = I x 2 ohms.
Now, divide 10 V by 2 ohms.
We get I = 5A.


Example 2


Now let’s say that you use the same battery of 10 V, but this time you know that the current flowing through the circuit is 1 ampere. Now you have to find the resistance. Let’s follow the above steps and put the given values in the equation.
This time our equation looks like 10 V = 1 A x R
Now divide 10 volts by 1 ampere.
This gives the value of R as10 ohms.


Example 3


For the last example, let’s take a battery whose voltage is unknown. This time you know that the current is 2 ampere while the resistance is 5 ohms. We will use the same equation to find the voltage of the battery.
When we put the given values in the above equation, it looks like V = 2 A x 5 ohms.
This gives the battery value as 10 V.
For the easy solving of these problems, use Ohm’s law Triangle, which is explained above.


Ohm’s Law Graph 

Conductor at constant temperature:

According to Ohm’s law, if a metallic conductor is at a constant temperature, then the current flowing through that conductor is directly proportional to the voltage across it with resistance as its constant proportionality. Let’s plot a graph by considering the above statement. For this graph let’s consider voltage across the conductor on the x-axis and current flowing through the conductor on the y-axis. On plotting this graph, we get a straight line as the result. The resistance of the conductor is the slope of this straight line graph. 

The slope of this graph is given by I/V = 1/R.

The rearrangement of slope in terms of constant resistance is given below

R = V/I.

Steps to draw ohm’s law graph with a constant temperature

  • Step 1: Take a graph paper and draw the x-axis and y-axis on it.
  • Step 2: Mark the x-axis as voltage and the y-axis as current.
  • Step 3: Now plot the values of voltage and current on the x-axis and y-axis respectively.
  • Step 4: Now connect the dots that are plotted on the graph.
  • Step 5: You will observe that when the dots are connected, we get a straight line on the graph. The straight line obtained represents the temperature of the conductor.

Conductor at different temperatures

In Ohm’s law, the temperature of the conductor is constant. The graph of the conductor temperature looks different than the graph with the conductor at a constant temperature. We get two straight lines on this graph.

Steps to draw ohm’s law graph for a conductor at different temperatures:

For this graph two different temperatures. Let’s consider the temperatures to be T1 and T2 respectively. Let the temperature T1 be greater than T2.

  • Step 1: Take a graph paper and draw the x-axis and y-axis on it.
  • Step 2: Mark the x-axis as voltage and the y-axis as current.
  • Step 3: Now plot the values of voltage and current for temperature T1 on the x-axis and y-axis respectively.
  • Step 4: Now connect the dots temperature T1 on the graph.
  • Step 5: Similarly, plot the values of voltage and current for the temperature T2 on the x-axis and y-axis respectively.
  • Step 6: Now connect the dots plotted on the graph for temperature T2.
  • Step 7: You will observe that there are two straight lines on the graph. These two straight lines represent the resistance of the conductor at temperatures t1 and t2 respectively.

Ohm’s law lab experiment

Aim

Ohm’s lab experiment is performed to determine the interrelationship between the current flowing through a resistor and potential difference across the same resistor of a conductor or circuit.

Apparatus

There are not many requirements for this experiment. The apparatus needed for this experiment are electric cells, resistors, an ammeter, a voltmeter, and some connecting wires.

Procedure

This experiment is distributed into two portions. For the first part, we will fluctuate the voltage across the resistor. The current through the circuit that is obtained will be noted. Similarly, for the second part, we will fluctuate the current flowing through the circuit. The voltage across the circuit that is obtained will be noted. With the help of this collected data of current and voltage across the circuit, the relationship between them can be examined.

Steps for the collection of varying voltage measurements across the circuit are as follows:

  • Step 1: According to the circuit diagram you have to set up the circuit. At first, add just one cell.
  • Step 2: Make sure to check your circuit before you turn the power on.
  • Step 3: Using the voltmeter measure the voltage across the resistor.
  • Step 4: Now, using the ammeter measure the current flowing through the circuit.
  • Step 5: Then add one more cell to the circuit and measure the current and voltage across the circuit.
  • Step 6: Repeat the procedure by adding one cell each time. Continue this until you have 4 cells.

Steps for the collection of varying voltage measurements across the circuit are as follows:

  • Step 1: According to the circuit diagram you have to set up the circuit. At first, add just one resistor.
  • Step 2: Make sure to check your circuit before you turn the power on.
  • Step 3: Using the voltmeter measure the voltage across the resistor.
  • Step 4: Now, using the ammeter measure the current flowing through the circuit.
  • Step 5: Then add one more resistor to the circuit and measure the current and voltage across the circuit.
  • Step 6: Repeat the procedure by adding one resistor each time. Proceed with this until your circuit has 4 resistors.
  • Step 7: Note all the readings into the following table: 

Observation and Results

For First Part:

VoltageCurrent
2.5 V0.1 A
5 V0.2 A
10 V0.4 A
15 V0.6 A

For Second Part:

CurrentVoltage
0.5 A2 V
1 A4 V
2 A8 V
3 A12 V

Analysis for varying voltage

For this analysis, we draw a graph that shows the relationship between current and voltage. Here, during the experiment variation in voltage is taken. So, the voltage is an independent variable. Since the current is dependent upon the voltage, it becomes the dependent variable. The independent variables are plotted on the x-axis while the dependent variable is plotted on the y axis. So we plot voltage on the x-axis and current on the y axis.

Analysis for varying current

For this analysis, we draw a graph that shows the relationship between voltage and current. Here, driving the experiment, variation in current is taken. So the current is the independent variable. Change the voltage is dependent on current become the dependent variable. The independent variables are plotted on the x-axis while the dependent variable is plotted on the y-axis. So we plot the current on the x-axis and voltage on the y-axis.

Conclusion

In the first part of the experiment, when the battery or cell is added, the ammeter reading increases with the increase in the reading of the voltmeter. Here, we get to know that when the voltage across the resistor is increased then the current also increases gradually.

Similarly in the second part of the experiment when a resistor is added, the reading of the voltmeter increases with an increase in the reading of the ammeter. Here, we get to know that when the current flowing through the resistor increased then the voltage also increases gradually.

From these observations, we can conclude that for voltage and current if one quantity increases, the other also increases whereas if one quantity decreases, the other increases simultaneously. This shows that the voltage across the conductor is directly proportional to the current flowing through the same conductor. This is what we name Ohm’s law. Therefore, this experiment verifies ohm’s law.


Ohm’s Law Lab Experimental use

The main applications of Ohm’s Law are given as follows:

  • The determination of voltage across the circuit, the current flowing through it, and the resistance applied are done with the help of Ohm’s Law. Some other factors like resistivity, drift speed, etc. are determined using these terms.
  • The power consumption can also be calculated using this law.
  • The voltage drop across the electronic components can be maintained according to your desire with the help of this law.
  • Diverting the current in the DC ammeter and other shunts is also done by using ohm’s law.

Use of Ohm’s Law in daily life

Besides the experimental use of ohm’s law, also has many empirical applications in various electrical components or appliances. Ohm’s law is significant. So we come across many of its applications in our day-to-day life. Some of these uses are explained below:

  1. Ohm’s law for controlling the speed of fans: The electric component with variable resistance is called the Potentiometer. Most of us know what is a potentiometer. This component is used for regulating the speed of a standard fan. The result can be achieved using a regulator or a circular knob. When the knob is rotated, the value of the resistance output component changes, as the knob is set up on the Potentiometer. The value of the resistance and current flowing can be calculated for a particular input resistance value. The power can be calculated using Ohm’s law.
  2. Wattage sizing required in electrical components: A large number of resistors are used for the operation of any electrical appliance such as an electric kettle, an iron, etc. Resistors help in the proper functioning of the appliance. With a proper wattage of these resistors, smooth functioning can be achieved. For this, the power can be calculated using P = V x I.
  3. Consumption and supply of power by an electronic device: To find the power of an electric heater, the coil in the heater and the voltage applied to it are used. After the calculation of power, the time for which the heater was used is multiplied. So the number of usage days is multiplied to it. this can help us to get the amount we need to pay as the electricity bill.
  4. Deciding fuses: A fuse is used to protect a circuit. We can use ohm’s law to decide which fuse to be used. It allows us to find the value of current flowing through the fuses as there connected in series with the appliance. You can select the fuse resistance is known or unknown. To protect your device or appliance from exploding, the current should be not too large.

Ohm’s Law Limitations:

  • As the unilateral electrical components like diodes, transistors, etc. allowed the current to flow through in only one direction, Ohm’s law cannot be applied to this network circuit.
  • It is difficult to use Ohm’s law in nonlinear electrical components which consist of capacitance, resistance, etc. This happens because the voltage and current won’t be constant in these electrical components.

Ohm’s Law Electric Power:

The rate at which the electrical energy of moving charges is converted into another form of energy is called electric power. Electrical energy can be converted into mechanical energy, heat, magnetic fields, etc.

The electric power can be measured by using the following formula:

P = V x I.

The unit of electric power of the circuit is given by Watt.

1 Watt is the power produced when a current of 1 ampere flows through a circuit across a potential difference of 1 volt. ‘W’ is used to denote Watt.

Ohm’s law can be used to calculate the electric power in terms of voltage, current, and resistance.

If voltage and current are given, we use

p = vI

If voltage and resistance are given, we use

     

         V2 
P =  ―
         R

If current and resistance are given, we use

p = I2  R

Ohm’s Law Power Triangle

The electric power triangle consists of voltage current and electric power. This triangle helps to solve the problems related to electric power easily. The use of this triangle is similar to ohm’s law equation triangle.

Ohm’s Law Power Triangle:
Ohm’s Law Power Triangle:

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