(a) Define (i) static resistance and (ii) dynamic resistance for an electrical…
PHYSICS · Subjective · CBSE · Physics · Current Electricity · Current Electricity
Problem
(a) Define (i) static resistance and (ii) dynamic resistance for an electrical element.
(b) A laboratory lamp with a tungsten filament is connected to a variable d.c. supply. As the applied voltage is slowly increased from zero, it is observed that the current at first rises rapidly but then increases more and more slowly. Explain qualitatively, on the basis of the temperature–dependence of resistance, why the V–I graph of the lamp is curved and why the lamp does not obey Ohm’s law.
(c) Sketch on the same set of axes the expected V–I characteristics for
(i) an ordinary metallic resistor that obeys Ohm’s law,
(ii) a forward-biased silicon diode.
Mark clearly the nature (linear or nonlinear) of each graph.