Question
A metal wire is subjected to a constant potential difference. When the temperature of the metal wire increases, the drift velocity of the electron in it
A.
increases, thermal velocity of the electron increases
B.
decreases, thermal velocity of the electron increases
C.
increases, thermal velocity of the electron decreases
D.
decreases, thermal velocity of the electron decreases
Answer :
decreases, thermal velocity of the electron increases
Solution :
When the temperature increases, resistance increases. As the $$e.m.f.$$ applied is the same, the current density decreases the drift velocity decreases. But the $$rms$$ velocity of the electron due to thermal motion is proportional to $$\sqrt T .$$ Therefore, the thermal velocity increases.