ohm triangle

An intro about Ohm’S LAW

Abstract

Ohm’s law is a significant law given by German scientist Georg Simon Ohm. The law is the relationship between three quantities i.e., Current, Resistance, and Voltage. Current is the flow of charges, Resistance is opposition to flow of current and Voltage is pressure from an electric circuit’s power. The current is measured in amperes (A), the voltage in volts (V), and resistance in units of ohms which is denoted by omega (Ω).

The formula of Ohm’s law is V=IR. We can calculate all three quantities from this single relation. This can be done by Ohm’s law triangle. Some devices that follow Ohm’s law are called ohmic devices and which don’t follow this law are called non-ohmic devices. We know, based on Ohm’s Law, V=I R, But R= ρl​ /A

Hence V= Iρl/A,       El=j l,  where σ = 1/ρ     Is known as the conductivity.

Ohm’s law can be used to find power by power triangle. This can be done by substituting values of current, voltage, and resistance into the formula of Ohm’s law.

To calculate power

[ P = V x I] P (watts) = V (volts) x I (amps)

[ P = V2 ÷ R]        P (watts) = V2 (volts) ÷ R (Ω)

The law is commonly used in everyday life operations and processes. As used in digital circuits, voltage divider circuits, thermostats, and regulators. Thus, the important law of life.

Ohm’s Law

Ohm’s Law is among the most fundamental and significant laws regulating electronic and electrical circuits. It relates current, voltage, and resistance for a linear device, such that if two understand, the third could be calculated.

With current, resistance, and voltage being three of the significant circuit quantities, this means that Ohm’s Law is also hugely significant.

Ohm’s Law is used within all branches of electronic and electrical science. It’s used for calculating the value of resistors required in circuits, and it can also be used for ascertaining the current flowing in a circuit in which the voltage could be measured easily across a known resistor, but more than that, Ohm’s Law is used in a huge number of calculations in all sorts of electric and electronic circuit- in fact anywhere that flows.

Georg Ohm

Georg Simon Ohm was a German physicist and mathematician. As a college teacher, Ohm started his study with the new electrochemical cell, invented by Italian scientist Alessandro Volta. Utilizing gear of his own creation, Ohm discovered that there’s a direct proportionality between the potential difference (voltage) applied across a conductor as well as the resultant electrical current. This relationship is called Ohm’s law.

Ohm’s Law

Ohm’s Law describes how current flows through a substance when different levels of voltage are implemented. Some substances like electric wires present little resistance to the flow and this sort of material is known as a conductor. Hence if this conductor is placed right across a battery by way of instance, plenty of current would flow.

In other cases, another substance may impede the flow of current, but still, allow some though. In electric circuits, these elements are often called resistors. Yet other substances let virtually no current though and these are called insulators.

Ohm’s Law Statement

The most basic elements of power are voltage, current, and resistance. Ohm’s law demonstrates a very simple relation between these three quantities. Ohm’s law states that the current through a conductor between two factors is directly proportional to the voltage across the two points.

Resistance

Resistance is a measure of the opposition to current flow in an electrical circuit. Measured in ohms, represented by the Greek letter omega (Ω). Ohms are named after Georg Simon Ohm.

Current

Current is the flow of electric charge carriers such as electrons. Electrical current flows from negative to positive points. The SI unit for measuring electrical current is the ampere (A). 1 ampere of current is described as one coulomb of electric charge moving past a special point in a second. Electric current is broadly used in household and industrial appliances.

Voltage

Voltage is the pressure from an electric circuit’s power source that pushes energized electrons (current) through a running loop, allowing them to perform work like illuminating a light.

In summary, voltage = pressure, and it’s measured in volts (V). The term acknowledges Italian physicist Alessandro Volta (1745-1827), inventor of the voltaic pile–the forerunner of the battery.

Further Reading:  Wave Motion and Relation of Wavelength with Velocity and Frequency
Ohm’s Law formula

Ohm’s Law formula or equation is extremely straightforward.

Ohm’s law can be demonstrated in a mathematical form:

V=IR

ohm formula

Where:

  • V = voltage shown in Volts
  • I = current shown in Amps
  • R = resistance shown in Ohms
Ohms Law Triangle

Transposing the Normal Ohms Law equation above will give us the following mixtures of the same equation:

ohm triangle

Then by using Ohms Law we can see a voltage of 1V applied to a resistor of 1Ω will cause a current of 1A to flow and the larger the resistance value, the less current which will flow for a given applied voltage.

ohmic devices

The system which follows ohm’s law for all voltages across it’s called an ohmic device. (i.e under continuous physical conditions like temperature, the resistance is constant for many currents that pass through it). Cases of ohmic devices are: a cable, heating element, or a resistor.

non-ohmic device

The system that doesn’t follow ohm’s law is called a non-ohmic apparatus (i.e. the resistance differs for different currents passing through it). Cases of non ohmic devices are: thermistors, crystal rectifiers, vacuum tube etc.

Derivation of Ohm’s Law

RELATION OF CURRENT DENSITY WITH ELECTRIC FIELD – FORMULA

We know, based on Ohm’s Law,

V=iR

But

R=ρl​ /A

Hence

V=Iρl/A

​Current per unit area (taken normal to the current), I/A, is called current density and is denoted by j.

Further, if E is the size of the uniform electric field in the conductor whose length is l, then the potential difference V across its ends is El.

El=jl

the above equation can also be casted in vector form. The current density (current through unit area normal to the present) is also guided along and can also be a vector J.

Hence the above equation can be casted in vector form as

E=σj​

​where σ= 1/ρIs known as the conductivity.

conductivity

Conductivity is the measure of the ease at which an electrical charge can pass through a material. A conductor is a material that gives hardly any resistance to the flow of an electric current.

VERIFYING OHM’S LAW – EXAMPLE

Let resistance used for verification be R. Create a circuit of R, voltmeter, and ammeter measuring voltage and current through R, rheostat (variable resistor), and a cell. Connect the components correctly. Note down values of voltage and current shown by voltmeter and ammeter. Repeat the above for different values of Rheostat. Record data in a tabular format and compute

I&V

For each instance. It should be roughly the same. Plot V v/s I on a chart paper. A straight line is obtained whose slope equals immunity.

ohm v sl

Electrical Power and Ohms Law

By using Ohm’s law and substituting for the values of V, R, and I the formula for Electric power Are Available as:

To find the Power (P)

[ P = V x I]      P (watts) = V (volts) x I (amps)

or:

[ P = V2 ÷ R]      P (watts) = V2 (volts) ÷ R (Ω)

or:

[ P = I2 x R]   P (watts) = I2 (amps) x R (Ω)

Again, the three quantities are superimposed to a triangle this time called a Power Triangle with electricity on top and voltage and current at the bottom. Again, this arrangement reflects the actual position of each quantity within the Ohms law power formulas.

The Power Triangle

ohm power triangle

Implementation of Ohm’s Law

There are thousands of uses of this law in our everyday life. We will show only some of them in this guide.

  • Traditional Domestic Fan Regulator is one very common device where the current through the fan gets regulated by controlling the resistance of the regulator circuit.
  • In a voltage divider circuit, this law is used to split source voltage across the output resistance.
  • In digital circuits, there are many functions where intentional voltage drop is required to supply specific voltage across different electronic elements. This is accomplished by applying Ohm’s law.

MCQs:

  • What is Ohm’s Law primarily concerned with?
    • A) Thermodynamics
    • B) Fluid dynamics
    • C) The relationship between current, voltage, and resistance
    • D) Chemical reactions
    • Answer: C
  • What are the three quantities involved in Ohm’s Law?
    • A) Velocity, force, and time
    • B) Pressure, temperature, and volume
    • C) Current, resistance, and voltage
    • D) Mass, acceleration, and distance
    • Answer: C
  • Which scientist is credited with the discovery of Ohm’s Law?
    • A) Isaac Newton
    • B) Albert Einstein
    • C) Georg Simon Ohm
    • D) Alessandro Volta
    • Answer: C
  • In Ohm’s Law, what does the symbol “V” represent?
    • A) Velocity
    • B) Voltage
    • C) Volume
    • D) Resistance
    • Answer: B
  • What is the SI unit for measuring electrical current?
    • A) Joule
    • B) Newton
    • C) Ampere
    • D) Coulomb
    • Answer: C
  • What is the formula for Ohm’s Law?
    • A) V = IR
    • B) P = IV
    • C) R = VI
    • D) P = VI
    • Answer: A
  • Which of the following statements is true regarding Ohm’s Law?
    • A) Current is inversely proportional to voltage
    • B) Resistance is inversely proportional to current
    • C) Voltage is directly proportional to current
    • D) Resistance is directly proportional to voltage
    • Answer: C
  • What is the symbol for resistance in Ohm’s Law?
    • A) R
    • B) V
    • C) I
    • D) A
    • Answer: A
  • Which component of an electrical circuit presents opposition to the flow of current?
    • A) Capacitor
    • B) Inductor
    • C) Resistor
    • D) Transformer
    • Answer: C
  • Which device follows Ohm’s Law for all voltages across it?
    • A) Capacitor
    • B) Diode
    • C) Resistor
    • D) Transformer
    • Answer: C
  • What does the term “current density” refer to?
    • A) The amount of charge stored in a conductor
    • B) The resistance of a material
    • C) The flow of current per unit area
    • D) The force exerted by moving charges
    • Answer: C
  • What is the measure of the ease at which an electrical charge can pass through a material?
    • A) Resistance
    • B) Conductivity
    • C) Voltage
    • D) Current
    • Answer: B
  • Which of the following is an example of a non-ohmic device?
    • A) Resistor
    • B) Thermistor
    • C) Heating element
    • D) Wire
    • Answer: B
  • What does the conductivity of a material indicate?
    • A) Its resistance to current flow
    • B) Its ability to store electrical charge
    • C) Its ease of allowing current to pass through
    • D) Its temperature coefficient
    • Answer: C
  • How can power be calculated using Ohm’s Law?
    • A) P = V × I
    • B) P = V² / R
    • C) P = I² × R
    • D) All of the above
    • Answer: D
  • What is the unit of power in electrical circuits?
    • A) Watt
    • B) Joule
    • C) Volt
    • D) Ampere
    • Answer: A
  • Which of the following devices regulates the current through a fan by controlling the resistance?
    • A) Transformer
    • B) Capacitor
    • C) Regulator
    • D) Rheostat
    • Answer: D
  • In what type of circuit is Ohm’s Law commonly used to split source voltage across the output resistance?
    • A) Series circuit
    • B) Parallel circuit
    • C) Complex circuit
    • D) Combination circuit
    • Answer: B
  • What is the primary purpose of using Ohm’s Law in digital circuits?
    • A) To increase voltage
    • B) To reduce current
    • C) To calculate power dissipation
    • D) To regulate temperature
    • Answer: C
  • What does a straight line obtained by plotting V v/s I on a chart paper represent?
    • A) Voltage drop
    • B) Current variation
    • C) Resistance
    • D) Power dissipation
    • Answer: C
Further Reading:  Photoelectric Effect with MCQs

 

FAQs about Ohm’s Law:

1. What is Ohm’s Law and why is it significant?

  • Ohm’s Law is a fundamental principle in electronics that relates the current, voltage, and resistance in a circuit. It’s significant because it allows engineers and scientists to understand and predict the behavior of electrical circuits.

2. Who discovered Ohm’s Law?

  • Ohm’s Law was discovered by the German physicist and mathematician Georg Simon Ohm.

3. What are the three quantities involved in Ohm’s Law?

  • The three quantities involved in Ohm’s Law are current (measured in amperes), voltage (measured in volts), and resistance (measured in ohms).

4. What is the formula for Ohm’s Law and how is it used?

  • The formula for Ohm’s Law is V = IR, where V represents voltage, I represents current, and R represents resistance. This formula is used to calculate any of the three quantities if the other two are known.

5. What is the significance of the Ohm’s Law triangle?

  • The Ohm’s Law triangle is a visual representation of the formula V = IR, which helps in easily calculating any of the three quantities (voltage, current, or resistance) by rearranging the formula.

6. What are ohmic devices and non-ohmic devices?

  • Ohmic devices are those that follow Ohm’s Law consistently across different voltages, while non-ohmic devices do not exhibit this linear relationship between voltage and current.
Further Reading:  Thermodynamics and Laws of Thermodynamics

7. How can Ohm’s Law be used to calculate power?

  • Ohm’s Law can be used to calculate power using formulas such as P = VI or P = V^2 / R, where P represents power, V represents voltage, and I represents current.

8. Can you explain the concept of conductivity in relation to Ohm’s Law?

  • Conductivity is a measure of how easily electrical charge can pass through a material. It is inversely related to resistance and is represented by the symbol σ in Ohm’s Law equations.

9. What are some practical applications of Ohm’s Law?

  • Ohm’s Law is used in various everyday applications, including voltage divider circuits, fan regulators, and digital circuits, where it helps in regulating current flow and determining voltage drops across components.

10. How can I verify Ohm’s Law experimentally?

  • Ohm’s Law can be verified experimentally by constructing a simple circuit with a known resistor, measuring the voltage and current across it, and repeating the process with different resistances to observe the relationship between voltage, current, and resistance.

Problem/Solutions about Ohm’s Law:

  1. Problem: A circuit has a resistance of 10 ohms and a current of 2 amperes flowing through it. Calculate the voltage across the circuit.
    Solution: Using Ohm’s Law (V = IR), where V is the voltage, I is the current, and R is the resistance: V = (2 A) * (10 Ω) = 20 V
  2. Problem: A resistor with a resistance of 100 ohms is connected to a 12-volt battery. Determine the current flowing through the resistor.

    Solution: Again, applying Ohm’s Law (V = IR): I = (12 V) / (100 Ω) = 0.12 A (or 120 mA)

  3. Problem: In a circuit, the current flowing through a resistor is 0.5 amperes, and the voltage across it is 6 volts. Calculate the resistance of the resistor.

    Solution: Rearranging Ohm’s Law to solve for resistance (R = V / I): R = (6 V) / (0.5 A) = 12 Ω

  4. Problem: A resistor has a resistance of 50 ohms, and a voltage of 10 volts is applied across it. Determine the power dissipated by the resistor.
    Solution: Using the formula for power in a circuit (P = V * I) or (P = V^2 / R): P = (10 V) * (10 V) / (50 Ω) = 20 W
  5. Problem: Verify Ohm’s Law experimentally using a resistor of known resistance. Measure the voltage and current across the resistor for different applied voltages.

    Solution: Set up a circuit with a resistor, voltmeter, ammeter, and power source. Record the voltage and current readings for various voltage settings. Plot a graph of voltage vs. current, and confirm that it forms a straight line, demonstrating the validity of Ohm’s Law.

Summary:

Ohm’s Law, established by the German scientist Georg Simon Ohm, forms the bedrock of understanding electrical circuits. It delineates the relationship between current (the flow of charges), voltage (the electrical pressure), and resistance (the opposition to current flow). Expressed as V = IR, where V represents voltage, I represents current, and R represents resistance, this law is instrumental in various applications across electronic and electrical sciences.

The Ohm’s Law triangle aids in facile calculation of any of the three quantities when the other two are known. Ohmic devices conform strictly to Ohm’s Law, maintaining consistent resistance across varying voltages, while non-ohmic devices exhibit resistance fluctuations with current variations.

The conductivity of a material, denoted by σ, inversely correlates with resistance, reflecting its ease for electrical charge passage. Verification of Ohm’s Law can be achieved through experimental setups involving the measurement of voltage and current across resistors of varying values.

Furthermore, Ohm’s Law extends to the computation of electrical power, offering formulas such as P = VI and P = V^2 / R. The Power Triangle visually represents these relationships, emphasizing the interplay between voltage, current, and power.

Ohm’s Law finds myriad applications in everyday life, from regulating current in fan regulators to facilitating intentional voltage drops in digital circuits. Its universality underscores its pivotal role in electrical engineering and technology.