For insulators and semiconductors, the resistance decreases with an increase in temperature because:
Number density of charge carriers increases
In semiconductors and insulators, resistance decreases with increasing temperature because:
- Unlike conductors, where increased temperature increases electron scattering, in semiconductors, heat excites more charge carriers (electrons and holes).
- More charge carriers reduce resistance as more free electrons are available to conduct electricity.
Thus, the correct answer is (b) Number density of charge carriers increases.
Important Questions from Ray Optics and Optical Instruments
The graph correctly representing the variation of image distance v for a convex lens of focal length f versus object distance u is:
Two slits are made 0.1 mm apart, and the screen is placed 2 m away. The fringe separation when a light of wavelength 500 nm is used is:
Resolving power of a telescope can be increased by increasing:
Match List - I with List - II.
List - I List - II (A) Contracting of Eye ball (I) Myopia (B) Controls the shape of eye lens (II) Cornea (C) Elongation of eye ball (III) Ciliary Muscle (D) Control the light entering in eyes (IV) Hypermetropia Choose the correct answer from the options given below:
Four lenses of focal length ±5cm and ±200cm are available for making a telescope. To produce the largest magnification, the focal length of the eyepiece should be:
