CBSE Class 12 Current Electricity Chapter 3 Notes Quiz

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Questions and Answers

What is the SI unit of current?

  • Ohm
  • Volt
  • Coulomb
  • Ampere (correct)

Which type of quantity is electric current?

  • Vector
  • Distance
  • Magnitude
  • Scalar (correct)

What is the cause of conductance in good conductors like metals?

  • Protons
  • Neutrons
  • Free electrons (correct)
  • Photons

In which direction does electric current flow with respect to the flow of positive charge?

<p>Same direction (D)</p> Signup and view all the answers

What is the relationship between current density and area of cross-section in a conductor?

<p>Direct relationship (B)</p> Signup and view all the answers

What is the relationship between drift velocity and mobility in a conductor?

<p>Directly proportional (A)</p> Signup and view all the answers

What does the temperature coefficient of resistance determine?

<p>How resistance varies with temperature (C)</p> Signup and view all the answers

In what situation would the resistance of a conductor double?

<p>When the length of the conductor is halved (D)</p> Signup and view all the answers

What happens to the resistivity of a material when it shows superconductivity?

<p>Drops to zero (B)</p> Signup and view all the answers

How is conductivity related to resistivity in a conductor?

<p>Directly proportional (D)</p> Signup and view all the answers

Flashcards

Ampere (A)

The SI unit of electric current, measuring the rate of flow of electric charge through a conductor.

Electrical Current

A scalar quantity that represents the rate of flow of electric charge through a conductor.

Conductance in Metals

The ability of a material to conduct electricity due to the presence of free electrons that can move easily through the material.

Current Flow and Positive Charge

The direction of electric current is the same as the direction of the flow of positive charge.

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Current Density and Area

Current density is directly proportional to the cross-sectional area of a conductor. This means a larger area allows for more current flow.

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Drift Velocity and Mobility

Drift velocity, the average velocity of electrons in a conductor, is directly proportional to the mobility of the electrons in the material.

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Temperature Coefficient of Resistance

The temperature coefficient of resistance determines how much the resistance of a material changes with temperature. Some materials increase resistance with increasing temperature, while others decrease.

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Resistance and Length

The resistance of a conductor doubles if its length is halved. This is because resistance is directly proportional to length.

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Resistivity in Superconductors

Superconductors have zero resistivity, meaning they allow current to flow with no resistance at all. This happens at very low temperatures.

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Conductivity and Resistivity

Conductivity is the reciprocal of resistivity. Higher conductivity means better electrical conduction.

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Study Notes

Electric Current

  • The SI unit of current is the ampere (A).
  • Electric current is a scalar quantity.

Conductance and Flow of Current

  • Good conductors like metals have high conductance due to the presence of free electrons.
  • Electric current flows in the direction of the flow of positive charge.

Current Density and Area of Cross-section

  • Current density is inversely proportional to the area of cross-section in a conductor.

Drift Velocity and Mobility

  • Drift velocity is directly proportional to mobility in a conductor.

Resistance and Temperature Coefficient

  • The temperature coefficient of resistance determines the change in resistance of a conductor with a change in temperature.
  • If the temperature coefficient of resistance is positive, the resistance of a conductor will double when the temperature is doubled.

Superconductivity

  • When a material shows superconductivity, its resistivity becomes zero.

Conductivity and Resistivity

  • Conductivity is the reciprocal of resistivity in a conductor.

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