Electronics and Communication Engineering - Materials and Components

11. 

The number of valence electrons in pentavalent impurity is

A. 5
B. 4
C. 3
D. 1

Answer: Option A

Explanation:

Pentavalent means 5 valence electrons.


12. 

If the diameter of a wire is doubled, its current carrying capacity becomes

A. one-fourth
B. half
C. twice
D. four times

Answer: Option D

Explanation:

Current carrying capacity depends on area of cross-section.


13. 

The law J = σE, where J is current density, σ is electrical conductivity and E is field strength is

A. Ohm's law
B. Gauss law
C. Ampere's law
D. Biot-Savart law

Answer: Option A

Explanation:

It is another form of Ohm's law.


14. 

Assertion (A): Silicon is less sensitive to changes in temperature than germanium.

Reason (R): Cut in voltage in silicon is less than that in germanium.

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

Answer: Option C

Explanation:

Cut in voltage of silicon is higher than that in germanium.


15. 

Material which lack permanent magnetic dipoles are known as

A. paramagnetic
B. diamagnetic
C. ferromagnetic
D. ferrimagnetic

Answer: Option B

Explanation:

Diamagnetic materials have no permanent magnetic diploes.