The relation between thermal conductivity K (W/m/�C), heat flow density Q (watt/

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Question
The relation between thermal conductivity K (W/m/�C), heat flow density Q (watt/m²) and dT/dx (�C per metre) is
Options
A. Q = K(dT/dx)
B. Q = - K(dT/dx)
C. K = Q(dT/dx)
D. dT/dx = - QK

Correct Answer

Q = - K(dT/dx)

Materials and Components problems

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1. An electron in a metal suffers collision and if the probability of it being scattered over an angle d? is 2p P(?) sin ? d? where P(?) is an arbitrary function of scattering angle ?, then
Options
A. 2pP(?) sin ? d? = 0
B. 2pP(?) sin ? d? = 2
C. 2pP(?) sin ? d? = -1
D. 2pP(?) sin ? d? = 1

5. Assertion (A): Doping level in extrinsic semiconductors is very small.
Reason (R): Additional of impurity in the ratio of 1 part in 10⁸ parts increases the number of charge carriers by about 20.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

6. Assertion (A): Ionic solids, in general, have no electrical conductivity.
Reason (R): In ionic solids, electrons are tightly bound to the nucleus.
Options
A. Both A and R are true and R is correct explanation of A
B. Both A and R are true but R is not correct explanation of A
C. A is true but R is false
D. A is false but R is true

9. When temperature is above ferromagnetic Curie temperature, a ferromagnetic material
Options
A. becomes a paramagnetic material
B. becomes a very strong ferromagnetic material
C. becomes diamagnetic material
D. none of the above

10. The number of turns in a coil is doubled. If initial time constant is T, the new time constant is
Options
A. T
B. 2T
C. 4T
D.

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