What is Ohm's Law: Definitions, Experiment, Examples

What is Ohm's Law

What is Ohm's Law:- Ohm’s Law, introduced by the German physicist Georg Simon Ohm, defines the relationship between current, voltage, and resistance in an electrical circuit. Formulated in 1827, Ohm's Law establishes that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it and the resistance (R) of the conductor. This can be mathematically represented as V = I * R.

Georg Simon Ohm discovered this principle through experiments, where he observed that the voltage drop across a conductor is determined by the product of the current passing through the conductor and its resistance. This fundamental law is pivotal in understanding and analyzing electrical circuits, making it essential for both theoretical and practical applications in physics and engineering. Know What is Ohm's Law, Ohm's Law Definition, Ohm's Law Experiment, Ohm's Law Examples etc.

Check out: Class 9th Books

Ohm's Law Definition

This law defines the relationship between voltage (V), current (I), and resistance (R) within an electrical circuit. According to Ohm's Law, the voltage across a conductor is directly proportional to the current flowing through it, with the proportionality constant being the resistance of the conductor. Mathematically, this relationship is expressed as V = I * R.

The significance of Ohm's Law lies in its simplicity and wide applicability. It provides a clear and straightforward method for calculating one of the three variables (voltage, current, resistance) if the other two are known. For instance, if the voltage and resistance in a circuit are known, the current can be calculated by rearranging the formula to I = V / R. Conversely, if the current and resistance are known, the voltage can be determined using V = I * R.

Ohm's Law is essential for designing and analyzing electrical and electronic circuits. It helps engineers and scientists understand how electrical components will behave under different conditions, ensuring the proper functioning of devices and systems. This law is also crucial for troubleshooting electrical problems, as it allows for the identification of issues such as excessive resistance or inadequate voltage supply.

Ohm’s Law Formula

Ohm's Law states that, provided all physical parameters and temperature remain constant, the voltage across a conductor is directly proportional to the current flowing through it.

Ohm’s Law can be expressed as:

Where:

• R is the constant of proportionality known as resistance,

• V is the voltage applied, and

• I is the current flowing through the electrical circuit.

Check out: CBSE Class 10th Books

Ohm’s Law Graph

Ohm’s Law is valid only when physical conditions, such as temperature, remain constant. This is because the current flowing through a circuit can change with variations in temperature. When factors like temperature influence the circuit, Ohm’s Law may not hold true. For instance, in a light bulb, the temperature increases as the current flow rises, causing deviations from Ohm’s Law.

Ohm’s Law Unit

Ohm's Law involves three key physical quantities:

• Current

• Voltage

• Resistance

Ohm’s Law Triangle

The Ohm's Law Triangle is a visual aid designed to help understand and remember the relationship between voltage, current, and resistance. This tool assists engineers in recalling how these three key quantities—current (I), voltage (V), and resistance (R)—are related.

 

Check out: School Books

Applications of Ohm’s Law

Ohm’s Law can be used to determine the voltage, current, impedance, or resistance in a linear electric circuit when any two of these quantities are known.

Main Applications of Ohm’s Law:

• Simplifying power calculations.

• Maintaining the desired voltage drop across electrical components.

• Determining the voltage, resistance, or current in an electric circuit.

• Redirecting current in DC ammeters and other DC shunts.

Ohm's Law Experiment

Conducting an Ohm's Law experiment involves verifying the relationship between voltage, current, and resistance in an electrical circuit. Here's a step-by-step guide on how to perform this experiment:

Objective:

To verify Ohm's Law by determining the relationship between voltage, current, and resistance in a circuit.

Materials Required:

• A DC power supply or a battery

• A resistor of known resistance

• A variable resistor (rheostat) or a set of different resistors

• Connecting wires

• A digital multimeter or ammeter and voltmeter

Procedure:

1. Set Up the Circuit:

• Connect the resistor to the circuit.

• Use the variable resistor or different fixed resistors to change the resistance.

• Connect the ammeter in series with the resistor to measure the current (I).

• Connect the voltmeter in parallel with the resistor to measure the voltage (V).

2. Connect the Power Supply:

• Connect the DC power supply to the circuit, ensuring all connections are secure.

• Begin with a low voltage setting to avoid damaging the resistor.

3. Take Measurements:

• Turn on the power supply and record the voltage across the resistor using the voltmeter.

• Simultaneously, record the current flowing through the circuit using the ammeter.

• Adjust the variable resistor to obtain different current readings, or replace it with resistors of different values to obtain a range of measurements.

4. Repeat the Process:

• For each different resistance or voltage setting, record the corresponding current and voltage readings.

• Ensure you take at least 5-10 sets of readings to get a comprehensive data set.

5. Data Analysis:

• Plot the recorded voltage (V) against the current (I) on a graph.

• According to Ohm's Law, the relationship should be linear, with the slope of the line representing the resistance (R).

• Verify if the slope of the line matches the known resistance value.

Conclusion:

If the plotted graph is a straight line passing through the origin, it confirms that voltage is directly proportional to current, validating Ohm’s Law. The slope of the line gives the resistance of the resistor, and it should be constant for a given resistor regardless of the current or voltage applied.

Check out: CBSE Class 12th Books

Limitations of Ohms Law

1. Non-Linear Components: Ohm's Law applies only to linear resistive components. For non-linear components like diodes and transistors, where resistance changes with voltage or current, Ohm's Law does not hold.

2. Variable Resistance with Temperature: In cases where the resistance of a material changes significantly with temperature (e.g., in light bulbs or thermistors), Ohm's Law may not accurately describe the behaviour.

3. High-Frequency Circuits: At high frequencies, reactive components such as capacitors and inductors become significant, and Ohm's Law, which is primarily applicable to resistive elements, may not fully describe circuit behaviour.

4. Non-Ohmic Materials: Materials that do not follow Ohm’s Law, known as non-ohmic materials, exhibit a non-linear relationship between voltage and current. These materials include many semiconductors and superconductors.

5. Circuit Conditions: Ohm's Law assumes ideal conditions such as perfect conductors and constant temperature. In real-world applications, factors like component tolerances, environmental conditions, and practical imperfections can affect the accuracy of Ohm's Law.

6. AC Circuits: In alternating current (AC) circuits, Ohm's Law needs to be adapted to account for impedance, which includes both resistance and reactance, making the relationship more complex than in DC circuits.

Ohm’s Law Examples

Example 1: If the resistance of an electric iron is 10 Ω and a current of 6 A flows through the resistance. Find the voltage between two points.

Solutions:-

Given:

I = 6 A, R = 10 Ω

The formula to calculate the voltage is given as:

V = I × R

⇒ V = 6 A × 10 Ω
⇒ V = 60 V

Hence, the voltage between two points is 60 V.

Example 2: A battery of 6 V is connected to the bulb of resistance 4 Ω. Find the current passing through the bulb and the circuit’s power.

Solutions:-

Given,
V = 6 V
R = 4 Ω

We know that,

V = IR    (Ohms Law)

⇒ 6 = 4R

⇒ I = 6 ÷ 4  = 1.5 A

⇒ I = 1.5 A

Thus, the current flowing through the bulb is 1.5 A

For the Power of the circuit

P = VI

⇒ P = (6)(1.5)

⇒ P = 9 watt

Thus, the power of the circuit is 9 watts.

What is Ohm's Law FAQs

1. What is Ohm's Law?

Ans. Ohm's Law states that the voltage (V) across a conductor is directly proportional to the current (I) flowing through it, with the resistance (R) being the constant of proportionality. Mathematically, it is expressed as:

𝑉=𝐼×𝑅

2. Who formulated Ohm's Law?

Ans. Ohm's Law was formulated by the German physicist Georg Simon Ohm in 1827.

3. What are the main components of Ohm's Law?

Ans. The main components of Ohm's Law are:

• Voltage (V)

• Current (I)

• Resistance (R)

4. How do you use Ohm's Law to calculate resistance?

Ans. To calculate resistance, rearrange the Ohm's Law formula to: 𝑅=𝑉𝐼. Divide the voltage by the current.

5. Can Ohm's Law be applied to all electrical components?

Ans. Ohm's Law applies primarily to linear, resistive components where the resistance remains constant. It does not apply to non-linear or reactive components, such as diodes, transistors, and capacitors.