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Updated on 17th July, 2023 , 11 min read
Ohm's law is a basic principle in electrical engineering which describes the relationship between current, voltage, and resistance in an electrical circuit. It states that the amount of current in a circuit is directly proportional to the voltage applied and inversely proportional to the resistance in the circuit. Georg Simon Ohm discovered Ohm's law through an experiment in 1826. He noticed that if the temperature is constant, the current flowing through a circuit is exactly proportional to the voltage and inversely proportional to the resistance. The relationship between electric current and potential difference is stated by Ohm's law. Most conductors' current is directly inversely proportional to the voltage applied to them. The German physicist Georg Simon Ohm was the first to experimentally confirm Ohm's law.
Ohm's Law asserts that, under normal circumstances and with a constant temperature, the potential difference at the ends of a metallic wire is precisely proportional to the current that flows through it.
Ohm's law is one of the most fundamental and significant laws governing electrical circuits.
Under the assumption that all physical parameters and temperatures remain constant, Ohm's law states that the voltage across a conductor is directly proportional to the current flowing through it.
To find the Voltage, ( V )
[ V = I x R ] V (volts) = I (amps) x R (Ω)
To find the Current, ( I )
[ I = V ÷ R ] I (amps) = V (volts) ÷ R (Ω)
To find the Resistance, ( R )
[ R = V ÷ I ] R (Ω) = V (volts) ÷ I (amps)
Resistance, abbreviated R in the equation, is the proportionality constant that has ohms as its unit of measurement, with the symbol Ω.
To students ofelectronics, Ohm's Law (E = IR) is as fundamentally important as Einstein's Relativity Equation (E = mc²) is to physicists.
When spelled out, it means voltage = current x resistance, or volts = amps x ohms, or V = A x Ω.
Only when the given temperature and the other physical variables remain constant does Ohm's law apply. Increasing the current causes the temperature to rise in some components. The filament of a light bulb serves as an illustration of this, where the temperature increases as the current increases. Ohm's law cannot be applied in this situation. The lightbulb filament violates Ohm's Law.
Quantity | Ohm's Law symbol | Unit of measure (abbreviation) | Role in circuits | In case you're wondering: |
Voltage | E | Volt (V) | Pressure that triggers electron flow | E = electromotive force (old-school term) |
Current | I | Ampere, amp (A) | Rate of electron flow | I = intensity |
Resistance | R | Ohm (Ω) | Flow inhibitor | Ω = Greek letter omega |
Note: Resistance cannot be measured in an operating circuit, so Ohm's Law is especially useful when it needs to be calculated. A technician can calculate R using the aforementioned application of Ohm's Law without having to shut off the circuit to measure resistance.
In order to calculate the remaining two symbols (see the middle pyramid above), X out the symbol for current (I) if you already know the voltage (E) and resistance (R) and want to know the current (I).
Additionally, you can calculate voltage (E) by multiplying the pyramid's bottom halves (see the third or far-right pyramid above) if you know the values of current (I) and resistance (R).
Try out a few simple series circuit calculations using just one voltage source (the battery) and one resistance source (the light). In each example, two values are known. The third can be calculated using Ohm's Law.
Similar Read: Brewster Law
Ohm's law is primarily utilized in:
The limitations of Ohm's law are as follows:
Ohm's Law describes the current flow through a resistance when various electric potentials (voltages) are applied to either end of the resistance. We cannot see electrons, so the water-pipe analogy helps us understand how electrical circuits work. Water flowing through pipes is a good mechanical system that can be compared to an electrical circuit.
The force acting on the pipe is represented by the voltage, the amount of water flowing through it is represented by the current, and the pipe's dimensions are represented by the resistance. Greater water flow through the pipe (current) will result from higher pressure (voltage) and a larger pipe (less resistance).
E = I x R = (5A)(8Ω) = 40 V
Ohm's main discovery when he published his formula in 1827 was that the voltage applied to a conductor directly relates to the amount of electric current flowing through it. In other words, it takes one volt of pressure to push through a resistance of one ohm.
The following experiment makes it simple to confirm Ohm's Law:
The static values of circuit components, current rates, voltage sources, and voltage drops can all be verified using Ohm's Law. A test instrument may indicate that resistance has decreased or voltage has increased, resulting in a high-voltage situation, if it detects, for instance, a higher than usual current measurement. This could indicate a supply or circuit issue.
A lower than usual current reading in a direct current (dc) circuit could indicate that the voltage has dropped or the circuit resistance has risen. Poor or loose connections, corrosion, and/or damaged components are potential causes of increased resistance.
Electrical current is drawn by the loads in a circuit. Any type of component, including small electrical devices, computers, home appliances, or a sizable motor, can be a load. The majority of these parts (loads) are marked with nameplates or informational stickers. These nameplates offer multiple references numbers and safety certification.
When learning about standard voltage and current values, technicians consult the nameplates on components. Technicians can use Ohm's Law to identify the component of a circuit that is failing and from there determine the potential location of a problem if they discover during testing that standard values do not register on their digital multimeters or clamp meters.
You can use the Ohm's law magic triangle to help you remember the various equations for solving for the different variables (V, I, and R).
If the voltage value is requested and the current and resistance values are provided, then the voltage can be calculated by simply covering V at the top. Thus, all that is left is the I and R or I R. So, the equation for voltage is current multiplied by resistance.
When we know the values of the other two parameters, we can use the power triangle to calculate the values of electric power, voltage, and current. Power (P) is at the top of the power triangle, while current (I) and voltage (V) are at the bottom.
The formula for calculating power when current and voltage values are given is,
The formula for calculating current when power and voltage values are given is,
The formula for calculating voltage when power and current values are given is,
The Ohm's law matrix table is a compact representation of the relationship between current (I), voltage (V), and resistance (R) in an electrical circuit. The table provides a quick reference for determining any one of the three variables if the other two are known.
The table below is a detailed explanation of each row and column:
Known Values | Resistance (R) | Current (I) | Voltage (V) | Power (P) |
Current & Resistance | - | - | R = I X R | P = I2 X R |
Voltage & Current | R = V/I | - | - | P = V X I |
Power & Current | R = P/I2 | - | V = P/I | - |
Voltage & Resistance | - | I = V/R | - | P = V2/R |
Power & Resistance | - | I = √P/R | V = √Z X R | - |
Voltage & Power | R = V2/P | I = P/V | - | - |
The Ohm's Law Pie Chart or Ohm's Law Wheel, which looks like the following, can be used to understand the relationship between the several parameters of Ohm's Law.
Electric power is the rate of energy conversion from the electrical energy of moving charges to other forms of energy such as mechanical energy, heat energy, energy stored in magnetic fields, or energy stored in electric fields. The watt is the measurement of power. Using Ohm's law and the values of voltage, current, and resistance as substitutes, the electrical power can be calculated.
Formula to find power
When the values for voltage and current are given,
When the values for voltage and resistance are given,
When the values for current and resistance are given,
Atoms make up all matter, including circuits. Atoms consist of subatomic particles:
The forces of attraction between an atom's nucleus and the electrons in its outer shell keep atoms joined together. Atoms in a circuit start to reform when voltage is applied, and the components of the circuit exert an attraction force known as a potential difference. Loose electrons that are attracted to one another move toward protons to form an electron current. Any material in the circuit that restricts this flow is considered resistance.
Ohm's law has a wide range of applications in electrical and electronics engineering. Some of the main uses of Ohm's law are:
Ans: According to Ohm's law,
V = R*I
So, 6 = 2(I)
or I = 6/2 = 3 A
Ans: Ohm's law does not apply to non-ohmic conductors, only to ohmic conductors like iron and copper, hence it cannot be said to be universally applicable.
Ans: According to Ohm's law,
V = R*I
So, 10 = R x 8
or, R = 10/8
R = 1.25 Ω
Ans: Given a 12 V battery, the task is to find the resistance such that the current will be limited to 0.04 A.
From Ohm's law,
V=IR
We solve for the resistance and substitute the given values,
R=V/Im
= 12 V/0.04 A
R = 300 Ω
Ans: Conductivity = 1/ resistivity
SI unit of conductivity = 1/ohmmeter
= ohm^{-1} m^{-1}
Ans: Ohm's Law has several applications, including the following:
Ans: Ohm's law does not account for the behaviour of unilateral devices like diodes and semiconductors. If the physical conditions, such as pressure and temperature, are not maintained constant, Ohm's law may also fail.
Ans: Ohm's Law was discovered by Georg Simon Ohm in 1826.
Ans: 1 Ohm is equal to one kilogramme metre squared per second cubed per ampere squared when converted to base units.
Ans: Ohm's law formula can be used in 3 forms –
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By - Nikita Parmar 2024-05-24 16:30:15 , 4 min readAccording to Ohm’s law, the voltage across two points is directly proportional to the current flowing through a conductor between them.
The static values of circuit components, such as current densities, voltage sources, and voltage drops, are verified using Ohm’s law.
The formula for Ohm’s law is V=IR.
The SI unit of electric resistance is the ohm (Ω).
The electrical resistance unit known by the abbreviation "ohm" is named after German physicist Georg Simon Ohm, who lived in the 19th century. It is measured in meters per kilogram per second.
Ohm’s Law is used in a wide range of electrical applications, from designing electronic circuits to calculating power consumption in household appliances. It is an essential tool for engineers and technicians working with electrical systems.
Ohm’s Law is used in a wide range of electrical applications, from designing electronic circuits to calculating power consumption in household appliances. It is an essential tool for engineers and technicians working with electrical systems.
Ohm’s Law is a fundamental tool in circuit analysis, allowing engineers to determine the current, voltage, or resistance of a circuit component by measuring the other two variables. It is often used to determine the power dissipated by a resistor or to calculate the voltage drop across a particular component.
In a series circuit, the current passing through each component is the same, and the voltage across each component is proportional to its resistance. In a parallel circuit, the voltage across each component is the same, and the current passing through each component is proportional to its conductance.
Ohm’s Law can be applied to AC circuits, but the analysis becomes more complicated due to the phase relationship between voltage and current. In AC circuits, the impedance, rather than the resistance, is used to describe the relationship between voltage and current. The impedance is a complex quantity that includes both resistance and reactance.