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Electric Resistance and OHM's Law

ICSE · Class 12 · Physics

Quick revision notes for Electric Resistance and OHM's Law — ICSE Class 12 Physics. Key concepts, formulas, and definitions for last-minute revision.

60 questions36 flashcards5 concepts

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Graphs showing the variation of resistivity with temperature for different types of materials: metals, semiconductors, and alloys.
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Key Topics to Revise

1

Electric Current and Current Density

  • Electric current is the rate of flow of charge through a conductor.
  • Current is a scalar quantity, so currents add arithmetically at a junction.
  • A conductor remains uncharged while current flows through it.
2

Free Electrons, Relaxation Time, Drift Velocity and Mobility

  • In metals, outer electrons leave their atoms and move freely through the substance as free electrons or conduction electrons.
  • Free electrons carry electrical energy from place to place.
  • The density of free electrons in metals is about 10^29 per m^3.
3

Ohm's Law, Resistance and Resistivity

  • Ohm's law states that potential difference is directly proportional to current when physical conditions remain constant.
  • Ohm's law is true for metallic conductors only.
  • Ohm's law is not universal.
4

Derivation of Ohm's Law and Microscopic Form

  • A metallic wire under potential difference has an electric field inside it.
  • The field produces acceleration of electrons opposite to the field direction.
  • Repeated collisions prevent continuous acceleration and produce a steady drift velocity.

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Full Notes

Key Concepts

Electric current is the rateCurrent density is the current perIn metalsRelaxation time is the average timeOhm's law states

Frequently Asked Questions

What are the important topics in Electric Resistance and OHM's Law for ICSE Class 12 Physics?
Electric Resistance and OHM's Law covers several key topics that are frequently asked in ICSE Class 12 board exams. Focus on the core concepts listed on this page and practise related questions to build confidence.
How to score full marks in Electric Resistance and OHM's Law — ICSE Class 12 Physics?
Understand the core concepts first, then work through the 60 practice questions available for this chapter. Revise formulas and definitions regularly, and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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