Ohm's law is valid only for currents following in:
Correct answer: A. Metallic conductor
- A. Metallic conductor
- B. Transistors
- C. Diodes
- D. Electric arcs
Explanation
Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points, assuming the temperature remains constant. This linear relationship (I = V/R) is valid primarily for metallic conductors. In contrast, transistors and diodes are semiconductor devices and exhibit nonlinear current-voltage characteristics, which means they do not follow Ohm's law. Electric arcs involve ionized gases (plasma), which also do not adhere to linear Ohmic behavior.
This question appeared on the ETEA MDCAT 2008 paper, which you can sit online with every answer explained.
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About Resistance and Resistivity
Resistance measures opposition to current in a conductor and follows R = V/I for an ohmic conductor, while resistivity is an intrinsic property of the material. Questions use R = ρL/A, examine effects of length, cross-sectional area and temperature, and distinguish resistance, resistivity, conductance and conductivity.
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