Which of the following are Ohmic materials?
Correct answer: D. Metals
- A. Semiconductors
- B. Tungsten filament
- C. Thermistor
- D. Metals
Explanation
Ohmic materials are those that follow Ohm's Law, where the resistance (R) is constant regardless of the applied voltage (V) or current (I). Metals, such as copper and aluminum, are typical examples of ohmic materials because they maintain a consistent resistance under typical conditions. In contrast, semiconductors, tungsten filaments, and thermistors do not maintain a constant resistance. Semiconductors have variable resistance due to their dependence on factors like doping, temperature, and voltage. Tungsten filaments change resistance with temperature increases. Thermistors are designed to have a resistance that varies with temperature. Hence, they are non-ohmic materials.
This question appeared on the ETEA MDCAT 2012 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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