When a material becomes a superconductor, its resistivity becomes
Answer: B
A superconductor has zero resistance.
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In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.
Answer: A
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Assertion (A): The optical dielectric constant (i.e., εr at optical frequencies)of ionic dielectrics is less than static dielectric constant.
Reason (R): At optical frequencies, Pi = 0.
Answer: A
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In a homogeneous magnetic field H of a solenoid, the core carries a magnetic dipole moment M per unit volume equal to
Answer: C
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In metals the thermal conductivity K and electrical conductivity σ are related as (K/σT) = L, L is known as
Answer: B
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Assertion (A): Helium, Argon and Neon are gaseous at room temperature.
Reason (R): The atoms in Helium, Argon and Neon are chemically extremely inactive.
Answer: A
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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.
Answer: C
Cut in voltage of silicon is higher than that in germanium.
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For a permanent magnetic material
Answer: A
Materials suitable for permanent magnet have large hysteresis loop.
Hence residual and coercive field are large.
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The hysteresis phenomenon in ferromagnetic materials exists at all temperatures.
Answer: B
Hysteresis phenomenon exists below ferromagnetic curie temperature.
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Assertion (A): For a magnetic material M = (μr - 1) H, where M is magnetic dipole moment/m3, H is field intensity A/m and μr is relative permeability.
Reason (R): μr can have any value from 0 to hundreds of thousands.
Answer: C
μr is always more than 1. It cannot be 0 or less than 1.
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