29
MCQ (Single Correct Answer)
Silicon doped with electron rich impurity forms ............ .
A
$p$-type semiconductor
B
n-type semiconductor
C
intrinsic semiconductor
D
insulator
30
MCQ (Single Correct Answer)
Which of the following statements is not true?
A
Paramagnetic substances are weakly attracted by magnetic field
B
Ferromagnetic substances cannot be magnetised permanently
C
The domains in antiferromagnetic substances are oppositely oriented with respect to each other
D
Pairing of electrons cancels their magnetic moment in the diamagnetic substances
31
MCQ (Single Correct Answer)
Which of the following is not true about the ionic solids?
A
Bigger ions form the close packed structure
B
Smaller ions occupy either the tetrahedral or the octahedral voids depending upon their size
C
Occupation of all the voids is not necessary
D
The fraction of octahedral or tetrahedral voids occupied depends upon the radii of the ions occupying the voids
32
MCQ (Single Correct Answer)
A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because .......... .
A
all the domains get oriented in the direction of magnetic field
B
all the domains get oriented in the direction opposite to the direction of magnetic field
C
domains get oriented randomly
D
domains are not affected by magnetic field
33
MCQ (Single Correct Answer)
The correct order of the packing efficiency in different types of unit cells is ............ .
A
fcc $<$ bcc $<$ simple cubic
B
fcc $>$ bcc $>$ simple cubic
C
fcc $<$ bcc $>$ simple cubic
D
$\mathrm{bcc}<\mathrm{fcc}>$ simple cubic