current electricity linear and non linear conductors

Learn linear and non linear conductors with Ohmic devices, non-Ohmic devices, V-I graphs, diodes, Zener diodes and exam-focused Current Electricity questions.

Current Electricity | Ohmic and Non-Ohmic Devices

Current Electricity - Linear and Non-Linear Conductors

current electricity linear and non-linear conductors are explained with V-I graphs, Ohmic devices, non-Ohmic devices, diodes, Zener diodes, filament bulbs, transistors, capacitors, inductors and exam-focused questions for CBSE, NEET, JEE Main, JEE Advanced, Olympiad, AP, IB, IGCSE and A-Level Physics.

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1. Formula Sheet First

V = IROhmic relation

I = V/RCurrent

R = V/IResistance

Slope of V-I = RVoltage on y-axis

Slope of I-V = 1/RCurrent on y-axis

J = σECurrent density

P = VIPower

P = I²RHeating

P = V²/RVoltage form

I = I₀(e^eV/kT - 1)Diode equation

I = C dV/dtCapacitor

V = L dI/dtInductor

Symbols: V = potential difference, I = current, R = resistance, J = current density, σ = conductivity, P = power, I₀ = reverse saturation current, C = capacitance, L = inductance.

2. What Are Linear Conductors?

Linear conductors have nearly constant resistance under fixed physical conditions. Their V-I graph is a straight line through the origin, so they obey Ohm's law.

Examples: metallic resistor, nichrome wire, manganin wire and constantan wire.

Exam point: the graph is linear only when temperature and physical conditions remain constant.

3. What Are Non-Linear Conductors?

Non-linear conductors have resistance that changes with voltage, current, temperature, light or internal carrier behaviour. Their V-I graph is curved, so they do not obey Ohm's law over the full range.

Examples: diode, Zener diode, LED, thermistor, filament bulb, transistor, triode and semiconductor devices.

Exam point: use dynamic resistance or graph interpretation instead of constant R.

4-5. Linear vs Non-Linear Conductors and Ohmic vs Non-Ohmic Devices

Point	Linear / Ohmic	Non-Linear / Non-Ohmic
Definition	V is directly proportional to I.	V and I are not directly proportional over full range.
V-I graph	Straight line through origin.	Curved or piecewise non-linear.
Resistance	Constant under fixed conditions.	Changes with V, I, temperature or bias.
Ohm's law	Valid at constant physical conditions.	Not valid over the full operating range.
Examples	Metal resistor, nichrome, manganin, constantan.	Diode, Zener, LED, thermistor, filament bulb, transistor.
Exam importance	Slope gives R directly.	Read graph carefully; use operating region.

Important note: all ideal linear conductors are ohmic under constant physical conditions, but practical devices can become non-linear at high current because heating changes resistance.

6-12. Device Behaviour and V-I Graphs

Resistor

A resistor is a linear conductor when temperature is constant. Example: if V doubles, I doubles.

Filament Bulb

Heating increases resistance, so current does not increase proportionally with voltage.

Diode

Forward current rises sharply after knee voltage; reverse current is small until breakdown.

Zener Diode

Works in reverse breakdown region and maintains nearly constant voltage for regulation.

LED

Forward biased non-linear device that emits light; it needs a series resistor.

Triode and Transistor-Like Devices

Show controlled, non-linear behaviour useful for amplification and switching.

Capacitor

I = C dV/dt; in DC steady state it behaves like open circuit.

Inductor

V = L dI/dt; it opposes change in current and has transient response.

13-17. Exam Question Bank With Accordion Solutions

Click each question to open the answer.

18. Common Student Mistakes

19. Final Revision Sheet

Linear conductor: constant R and straight V-I graph.

Non-linear conductor: changing R and curved graph.

Ohmic device: obeys Ohm's law under fixed conditions.

Non-ohmic device: diode, LED, Zener, bulb, thermistor.

V-I slope: resistance when V is y-axis.

I-V slope: conductance when I is y-axis.

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