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Answer the following questions:
(a) A steady current flows in a metallic conductor of nonuniform cross-section. Which of these quantities is constant along the conductor: current, current density, electric field, drift speed?
(b) Is Ohm's law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm's law.
(c) A low voltage supply from which one needs high currents must have very low internal resistance. Why?
(d) A high tension (HT) supply of say, $6 \mathrm{kV}$ must have a very large internal resistance. Why?
(a) A steady current flows in a metallic conductor of nonuniform cross-section. Which of these quantities is constant along the conductor: current, current density, electric field, drift speed?
(b) Is Ohm's law universally applicable for all conducting elements? If not, give examples of elements which do not obey Ohm's law.
(c) A low voltage supply from which one needs high currents must have very low internal resistance. Why?
(d) A high tension (HT) supply of say, $6 \mathrm{kV}$ must have a very large internal resistance. Why?
Solution:
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Verified Answer
(a) Only current (because it is given to be steady!). The rest depends on the area of cross section inversely.
(b) No, examples of non-ohmic elements vacuum diode, semiconductor diode etc.
(c) Because the maximum current drown from source is equal to $\varepsilon / r$.
(d) Because, if the circuit is shorted (accidentally), the current drown will exceed safety limits, if internal resistance is not large.
(b) No, examples of non-ohmic elements vacuum diode, semiconductor diode etc.
(c) Because the maximum current drown from source is equal to $\varepsilon / r$.
(d) Because, if the circuit is shorted (accidentally), the current drown will exceed safety limits, if internal resistance is not large.
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