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Electric Resistance and OHM's Law — Revision Notes

ICSE · Class 12 · Physics

Electric Resistance and OHM's Law revision notes for ICSE Class 12 Physics: 4 topics in quick points. Part of the ICSE Class 12 Physics syllabus.

60 questions36 flashcards18 formulas & key relations5 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?
Key topics in Electric Resistance and OHM's Law include Electric Current and Current Density, Free Electrons, Relaxation Time, Drift Velocity and Mobility, Ohm's Law, Resistance and Resistivity, Derivation of Ohm's Law and Microscopic Form. Study these first, then practise questions on each for the ICSE Class 12 board exam.
How should I revise Electric Resistance and OHM's Law for the ICSE Class 12 board exam?
Learn the core ideas first, then work through the 60 practice questions on Electric Resistance and OHM's Law. Revise 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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