Current Density Relation
Mediumphysics
Current density J relates to conductivity σ and electric field E by?
Select the correct option:
Solution
Incorrect! Answer:
J = σ E
- Microscopic Form of Ohm's Law: While V=IR is macroscopic, J=σE describes conduction at a point.
- Definitions:
- J=I/A (Current density)
- E=V/L (Electric field)
- Derivation:
- V=IR⟹EL=JA×(ρL/A)
- EL=JρL⟹E=Jρ
- J=E/ρ
- Final Step: Since 1/ρ=σ, we get J=σE.
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About This Question
- Subject
- physics
- Chapter
- current electricity
- Topic
- current density relation
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
J = σ E
- Microscopic Form of Ohm's Law: While V=IR is macroscopic, J=σE describes conduction at a point.
- Definitions:
- J=I/A (Current density)
- E=V/L (Electric field)
- Derivation:
- V=IR⟹EL=JA×(ρL/A)
- EL=JρL⟹E=Jρ
- J=E/ρ
- Final Step: Since 1/ρ=σ, we get J=σE.
This medium difficulty physics question is from the chapter current electricity, covering the topic of current density relation. It appeared in the 2025 exam.
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