Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, ther

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Question
Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.
Reason (R): Thermionic emission current ? T² e^-Ew/kT.
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

Correct Answer

Both A and R are true and R is correct explanation of A

Materials and Components problems

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1. The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called
Options
A. Weiss temperature
B. Curie temperature
C. Neel temperature
D. None of the above

2. Assertion (A): If W_F is Fermi energy, v is velocity of electron and m is mass of electron, then .
Reason (R): Conductivity of a metal depends on temperature and impurity concentration.
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

3. For a photoconductor with equal electron and hole mobilities and perfect ohmic contacts at the ends, an increase in intensity of optical illumination results in
Options
A. a change in o.c voltage
B. a change in s.c current
C. decrease in resistance
D. increase in resistance

5. If q is charge on an electron, R is radius of electron orbit and ? is angular velocity of electron rotation, the magnetic dipole moment of electron in orbit is
Options
A. 0.5 q?R
B. 0.5 q²?²R²
C. 0.5 q?R²
D. 0.5 q?²R

6. Assertion (A): Silicon is the most favoured semiconductor material.
Reason (R): PIV for silicon diode is more than that for germanium diode.
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

7. Assertion (A): Magnetism can be explained by the theory of magnetic domains.
Reason (R): The existence of magnetic domains is evident from the Bitter powder patterns.
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

10. In a piezoelectric crystal, the application of mechanical force will cause
Options
A. plastic deformation of crystal
B. magnetic dipoles in the crystal
C. electrical polarization in the crystal
D. shift in Fermi level

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