Do bends in a wire impact its resistance?

No, bends in a wire do not affect its resistance because the mean free path of electrons is shorter than the bend's radius, allowing them to navigate around it easily. As long as the cross-sectional area remains constant, resistance remains unchanged.

How is current maintained as a continuous flow within a conductor?

By maintaining a voltage difference between the two ends of the conductor.

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Ohm's Law

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Ohm’s Law

Ohm's Law is a key principle in electrical engineering and physics that defines the relationship between voltage, current, and resistance within an electrical circuit. Developed by the German physicist Georg Simon Ohm in the 1820s, this law offers a straightforward mathematical framework for understanding the interactions among electrical components.

Serving as the cornerstone of electrical theory, Ohm's Law enables us to anticipate circuit behaviour under various conditions and plays a crucial role in the design and advancement of diverse electrical devices and technologies.

1.0Statements of Ohm’s Law

In Physical quantities like temperature, pressure, volume, length, cross-section or nature of the material kept constant, then current through a conductor is directly proportional to potential difference applied across it. This is called Ohm’s Law.

V ∝ I

VI=Constant=R (Resistance)

V ∝ I

V =IR

R is called the resistance of the conductor.

S.I Unit of R - Ohm

Slope = $\frac{V}{I} = Tan θ = R$

$I \propto V$

I=G V

G $is called the conductance of conductor$

$S.I Unit of G \Rightarrow mh o (Ω^{- 1}) or Siemens$

Conductance G from the slope of a VI graph

$Sl o p e = \frac{I}{V} = Tan θ = G$

2.0Proof of Ohm’s Law

From microscopic forms of Ohm’s Law

$J = σ E$

$\frac{I}{A} = σ (\frac{V}{l})$

$\frac{V}{I} = (\frac{1}{σ}) \times \frac{l}{A} = ρ \times \frac{l}{A}$

$[Where ρ = \frac{1}{σ} = \frac{m}{n e ^{2} τ}]$

$\frac{V}{I} = R \Rightarrow Ohm’s Law$

$R = \frac{ρl}{A} = Resistance [SI Unit of ρ is ohm - m]$

Where $l is the length of the conductor and$

$A is the area of cross - section,$

$ρ is the resistivity or specific resistance.$

Related Video:

3.0Microscopic Form Of Ohm’s Law

Relation between $J, σ and E$
For an Electron q=-e

$v_{d} = - \frac{e E τ}{m}$

$J = n q v_{d} = n (- e) (- \frac{e E τ}{m}) = \frac{n e ^{2} τ}{m} E$

$(\frac{n e ^{2} τ}{m} = \frac{1}{ρ} = σ = Conductivity of conductor)$

$J = σ E or E = ρ J$

4.0Experimental Verification of Ohm’s Law

Ohm's Law can be verified through a simple experiment that demonstrates the relationship between voltage, current, and resistance in a circuit. The procedure involves measuring current through a resistor at different voltage levels using the following equipment:
Power Supply-Variable DC supply or battery, Resistor- Known value (e.g., 100 Ω), Ammeter- Measures current (A), Voltmeter- Measures voltage (V) ,Connecting Wires, Breadboard
To set up the circuit, connect the resistor in series with the ammeter and power supply, ensuring that the voltmeter is connected across the resistor. Begin the experiment by setting the power supply to a low voltage and recording the current (I) and voltage (V) readings. Next, gradually increase the voltage in increments and note the corresponding current for each level. Finally, compile the data into a table to organise the recorded voltage (V) and current (I) values for analysis.
Calculate Resistance: $\frac{V}{I} = R \Rightarrow Ohm’s Law$ , to calculate resistance for each voltage-current pair. The resistance should remain consistent.
Graphing: Plot voltage (V) on the y-axis and current (I) on the x-axis. A straight line indicates a direct proportionality, confirming Ohm's Law.
The experiment should demonstrate that as voltage increases, current also rises linearly, validating Ohm's Law and emphasising the predictable nature of electrical circuits.

5.0V – I Characteristics (Linear and Non-linear)

Linear V-I characteristics

At fixed temperature, current is directly proportional to the applied potential difference. This law is called ohm's law and substances which obey it are called ohmic or linear conductors.

Non- Linear V-I characteristics

The relation between V and I relies on the signifier of V. In other words, if I is the current for a certain V, then flipping the direction of V, keeping its strength fixed, does not produce a current of the same magnitude as I in the opposite direction (Figure 1).

The relation between V and I is not distinctive, i.e., there is more than one value of V for the same current I (Figure 2). A material exhibiting such a behaviour is GaAs.

6.0Limitations of Ohm’s Law

The straight line V-I graph does not pass through the origin.
V-I relationship is non-linear
V-I relationship leans on the sign of V for the same absolute value of V
V-I relationships are not unique.
Examples of non-ohmic conductors are water voltameter, p-n junction diode, thyristor.

7.0Applications of Ohm’s Law

It aids students in calculating voltage, current, and resistance in simple series and parallel circuits, allowing them to understand how components function under various conditions.
It is used to design basic electrical circuits, calculating the necessary resistor values to ensure household appliances operate safely and efficiently.
Ohm's Law is essential for electrical safety, as it helps to calculate the maximum allowable current in circuits to avoid overheating and hazards.

8.0Ohm’s Law Triangle

The Ohm's Law triangle is a useful visual aid that illustrates the relationship between voltage (V), current (I), and resistance (R) in electrical circuits. Arranged in a triangular format, voltage is placed at the top, while current and resistance are positioned at the bottom corners.
Voltage (V): Multiply current (I) by resistance (R):V=I R
Current (I): Divide voltage (V) by resistance (R): $I = \frac{V}{R}$
Resistance (R): Divide voltage (V) by current (I): $R = \frac{V}{I}$

9.0Sample Questions on Ohm’s Law

Q-1.In the shown I-V Curve Calculate $\frac{R _{1}}{R _{2}}$ .

Solution: Slope of given graphs gives conductance (G)

$Tan 6 0^{\circ} = G_{1} = 3 = \frac{1}{R _{1}}, R_{1} = \frac{1}{3}$

$Tan 3 0^{\circ} = G_{2} = \frac{1}{3} = \frac{1}{R _{2}}, R_{2} = 3$

$\frac{R _{1}}{R _{2}} = \frac{\frac{1}{3}}{3} = \frac{1}{3}$

Q-2.The voltage-current graphs for two resistors of the same material and the same radius with lengths,L₁ and L₂ are shown in figure. If L₁ > L₂, state with reason which of these graphs represents voltage current change for L₁.

Solution: As, $R_{A} = \frac{V}{I _{A}}$ and $R_{B} = \frac{V}{I _{B}}$

$\frac{I _{A}}{I _{B}} = \frac{R _{B}}{R _{A}}$

Fom figure as $I_{A} > I_{B^{'}} R_{B} > R_{A}$ Since $R \propto L$ Graph B represents the voltage current change for $L_{1}$

Q-3.The I-V characteristics of a resistor is monitored to deviate from a straight line for higher value of current as shown in figure Why?

Solution: For higher value of current, the resistor gets heated and consequently its resistance increases. The resistor becomes non-ohmic due to which the I-V characteristic deviates from the straight line thereby showing lesser current for the same voltage.

Also Read:

Ampere's Law	Maximum Power Transfer Theorem	Carbon Resistor
Current Electricity	Batteries in Series and Parallel	Difference Between Resistance And Resistivity
Meter Bridge	Kirchhoff's law	Current Density

Join ALLEN!

(Session 2026 - 27)

Name

Mobile Number

Class

Choose class

Goal

Choose your goal

Preferred Programs

Preferred Mode

State

Choose State

I agree to

I authorise ALLEN Career Institute Pvt Ltd to send me regular updates via Phone calls, Whatsapp, SMS, Robocalls (Automated Calls), Emails, or on postal address.

Ohm’s Law

Ohm's Law is a key principle in electrical engineering and physics that defines the relationship between voltage, current, and resistance within an electrical circuit. Developed by the German physicist Georg Simon Ohm in the 1820s, this law offers a straightforward mathematical framework for understanding the interactions among electrical components.

Serving as the cornerstone of electrical theory, Ohm's Law enables us to anticipate circuit behaviour under various conditions and plays a crucial role in the design and advancement of diverse electrical devices and technologies.

1.0Statements of Ohm’s Law

In Physical quantities like temperature, pressure, volume, length, cross-section or nature of the material kept constant, then current through a conductor is directly proportional to potential difference applied across it. This is called Ohm’s Law.

V ∝ I

VI=Constant=R (Resistance)

V ∝ I

V =IR

R is called the resistance of the conductor.

S.I Unit of R - Ohm

Slope = $\frac{V}{I} = Tan θ = R$

$I \propto V$

I=G V

G $is called the conductance of conductor$

$S.I Unit of G \Rightarrow mh o (Ω^{- 1}) or Siemens$

$Sl o p e = \frac{I}{V} = Tan θ = G$

2.0Proof of Ohm’s Law

From microscopic forms of Ohm’s Law

$J = σ E$

$\frac{I}{A} = σ (\frac{V}{l})$

$\frac{V}{I} = (\frac{1}{σ}) \times \frac{l}{A} = ρ \times \frac{l}{A}$

$[Where ρ = \frac{1}{σ} = \frac{m}{n e ^{2} τ}]$

$\frac{V}{I} = R \Rightarrow Ohm’s Law$

$R = \frac{ρl}{A} = Resistance [SI Unit of ρ is ohm - m]$

Where $l is the length of the conductor and$

$A is the area of cross - section,$

$ρ is the resistivity or specific resistance.$

Related Video:

3.0Microscopic Form Of Ohm’s Law

Relation between $J, σ and E$
For an Electron q=-e

$v_{d} = - \frac{e E τ}{m}$

$J = n q v_{d} = n (- e) (- \frac{e E τ}{m}) = \frac{n e ^{2} τ}{m} E$

$(\frac{n e ^{2} τ}{m} = \frac{1}{ρ} = σ = Conductivity of conductor)$

$J = σ E or E = ρ J$

4.0Experimental Verification of Ohm’s Law

Ohm's Law can be verified through a simple experiment that demonstrates the relationship between voltage, current, and resistance in a circuit. The procedure involves measuring current through a resistor at different voltage levels using the following equipment:
Power Supply-Variable DC supply or battery, Resistor- Known value (e.g., 100 Ω), Ammeter- Measures current (A), Voltmeter- Measures voltage (V) ,Connecting Wires, Breadboard
To set up the circuit, connect the resistor in series with the ammeter and power supply, ensuring that the voltmeter is connected across the resistor. Begin the experiment by setting the power supply to a low voltage and recording the current (I) and voltage (V) readings. Next, gradually increase the voltage in increments and note the corresponding current for each level. Finally, compile the data into a table to organise the recorded voltage (V) and current (I) values for analysis.
Calculate Resistance: $\frac{V}{I} = R \Rightarrow Ohm’s Law$ , to calculate resistance for each voltage-current pair. The resistance should remain consistent.
Graphing: Plot voltage (V) on the y-axis and current (I) on the x-axis. A straight line indicates a direct proportionality, confirming Ohm's Law.
The experiment should demonstrate that as voltage increases, current also rises linearly, validating Ohm's Law and emphasising the predictable nature of electrical circuits.

5.0V – I Characteristics (Linear and Non-linear)

Linear V-I characteristics

At fixed temperature, current is directly proportional to the applied potential difference. This law is called ohm's law and substances which obey it are called ohmic or linear conductors.

Non- Linear V-I characteristics

The relation between V and I relies on the signifier of V. In other words, if I is the current for a certain V, then flipping the direction of V, keeping its strength fixed, does not produce a current of the same magnitude as I in the opposite direction (Figure 1).

The relation between V and I is not distinctive, i.e., there is more than one value of V for the same current I (Figure 2). A material exhibiting such a behaviour is GaAs.

6.0Limitations of Ohm’s Law

The straight line V-I graph does not pass through the origin.
V-I relationship is non-linear
V-I relationship leans on the sign of V for the same absolute value of V
V-I relationships are not unique.
Examples of non-ohmic conductors are water voltameter, p-n junction diode, thyristor.

7.0Applications of Ohm’s Law

It aids students in calculating voltage, current, and resistance in simple series and parallel circuits, allowing them to understand how components function under various conditions.
It is used to design basic electrical circuits, calculating the necessary resistor values to ensure household appliances operate safely and efficiently.
Ohm's Law is essential for electrical safety, as it helps to calculate the maximum allowable current in circuits to avoid overheating and hazards.

8.0Ohm’s Law Triangle

The Ohm's Law triangle is a useful visual aid that illustrates the relationship between voltage (V), current (I), and resistance (R) in electrical circuits. Arranged in a triangular format, voltage is placed at the top, while current and resistance are positioned at the bottom corners.
Voltage (V): Multiply current (I) by resistance (R):V=I R
Current (I): Divide voltage (V) by resistance (R): $I = \frac{V}{R}$
Resistance (R): Divide voltage (V) by current (I): $R = \frac{V}{I}$

9.0Sample Questions on Ohm’s Law

Q-1.In the shown I-V Curve Calculate $\frac{R _{1}}{R _{2}}$ .

Solution: Slope of given graphs gives conductance (G)

$Tan 6 0^{\circ} = G_{1} = 3 = \frac{1}{R _{1}}, R_{1} = \frac{1}{3}$

$Tan 3 0^{\circ} = G_{2} = \frac{1}{3} = \frac{1}{R _{2}}, R_{2} = 3$

$\frac{R _{1}}{R _{2}} = \frac{\frac{1}{3}}{3} = \frac{1}{3}$

Q-2.The voltage-current graphs for two resistors of the same material and the same radius with lengths,L₁ and L₂ are shown in figure. If L₁ > L₂, state with reason which of these graphs represents voltage current change for L₁.

Solution: As, $R_{A} = \frac{V}{I _{A}}$ and $R_{B} = \frac{V}{I _{B}}$

$\frac{I _{A}}{I _{B}} = \frac{R _{B}}{R _{A}}$

Fom figure as $I_{A} > I_{B^{'}} R_{B} > R_{A}$ Since $R \propto L$ Graph B represents the voltage current change for $L_{1}$

Q-3.The I-V characteristics of a resistor is monitored to deviate from a straight line for higher value of current as shown in figure Why?

Solution: For higher value of current, the resistor gets heated and consequently its resistance increases. The resistor becomes non-ohmic due to which the I-V characteristic deviates from the straight line thereby showing lesser current for the same voltage.

Also Read:

Ampere's Law	Maximum Power Transfer Theorem	Carbon Resistor
Current Electricity	Batteries in Series and Parallel	Difference Between Resistance And Resistivity
Meter Bridge	Kirchhoff's law	Current Density

Frequently Asked Questions

Do bends in a wire impact its resistance?

How is current maintained as a continuous flow within a conductor?

Frequently Asked Questions

Do bends in a wire impact its resistance?

How is current maintained as a continuous flow within a conductor?

Join ALLEN!

Ohm’s Law

1.0Statements of Ohm’s Law

2.0Proof of Ohm’s Law

3.0Microscopic Form Of Ohm’s Law

4.0Experimental Verification of Ohm’s Law

5.0V – I Characteristics (Linear and Non-linear)

6.0Limitations of Ohm’s Law

7.0Applications of Ohm’s Law

8.0Ohm’s Law Triangle

9.0Sample Questions on Ohm’s Law

Table of Contents

Join ALLEN!

Ohm’s Law

1.0Statements of Ohm’s Law

2.0Proof of Ohm’s Law

3.0Microscopic Form Of Ohm’s Law

4.0Experimental Verification of Ohm’s Law

5.0V – I Characteristics (Linear and Non-linear)

6.0Limitations of Ohm’s Law

7.0Applications of Ohm’s Law

8.0Ohm’s Law Triangle

9.0Sample Questions on Ohm’s Law

Table of Contents