Recent questions and answers in Physics

2 answers 29 views

In a metal wire, which particle carries electric current?

answered Aug 15, 2018 in Physics
1 answer 20 views

If temperature of a pure silicon specimen is increased, then (a) only number of free electrons increase. (b) only number of free holes increase. (c) number of free holes and free electrons increases. (d) only number of free holes decrease. 

answered Aug 11, 2018 in Physics
1 answer 9 views

In which material, valence electrons are tightly bounded to their parent atoms ? (a) Conductor (b) Semiconductor (c) Insulator (d) Magnetic 

answered Aug 11, 2018 in Physics
1 answer 17 views

Ferrites are types of (a) magnetic material (b) conducting material (c) semiconducting material (d) insulating material

answered Aug 11, 2018 in Physics
2 answers 33 views

If an atom loses one or more electrons, it becomes _____.

answered Aug 11, 2018 in Physics
3 answers 34 views

A radioactive isotope has a half-life of 10 days. If today there are 125 g of it left, what was its original weight 40 days earlier  (a) 600 g (b) 1000 g (c) 1250 g (d) 2000 g 

answered Jul 22, 2018 in Physics
1 answer 9 views

The correct order of electromagnetic spectrum with decreasing frequency is: (1) Microwaves, Radiowaves, Infrared rays, Ultraviolet rays, X–rays (2) Radiowaves, Infrared rays, Ultraviolet rays, Microwaves, X–rays (3) X–rays, Infrared rays, Microwaves, Radiowaves, Ultraviolet rays (4) X–rays, Ultraviolet rays, Infrared rays, Microwaves, Radiowaves 

answered May 29, 2018 in Physics
0 answers 10 views

Moving coil instruments have which one of the following scales ? (a) Logarithmic scale (b) Uniform scale (c) Non-uniform scale (d) Squared scale 

asked May 26, 2018 in Physics
0 answers 8 views

Super conducting materials can be used for (a) ore refining. (b) magnetic levitation in high speed trains. (c) medical resonance imaging. (d) All of the above  

asked May 26, 2018 in Physics
0 answers 12 views

A silicon p-n junction at a temperature of 20 °C has a reverse saturation current of 10 pA. The reverse saturation current at 40 °C will approximately be (a) 30 pA (b) 40 pA (c) 50 pA (d) 60 pA

asked May 25, 2018 in Physics
0 answers 19 views

A material has conductivity of 10–2 mho/m and relative permittivity of 4. The frequency at which the conduction current in the medium is equal to the displacement current, is (a) 450 MHz (b) 900 MHz (c) 45 MHz (d) 90 MHz

asked May 25, 2018 in Physics
0 answers 13 views

Both donor and acceptor impurities are present in the combination of (a) Phosphorous - Arsenic (b) Aluminium - Antimony (c) Boron - Gallium (d) Arsenic - Antimony

asked May 25, 2018 in Physics
0 answers 30 views

A cable has an insulation of relative permittivity 2. If the insulation is replaced by one of relative permittivity 4, then capacitance of the cable (a) is doubled (b) is halved (c) remains unchanged (d) is reduced 

asked May 25, 2018 in Physics
0 answers 107 views

Three materials X, Y and Z having relative permittivity 2.5, 3.0 and 4.0 respectively are used in a single core cable. The materials on inner most and outer most layer respectively should be (a) X and Y (b) Y and Z (c) X and Z (d) Z and X 

asked May 25, 2018 in Physics
0 answers 12 views

If temperature of a radiating body is 1500 °C, the wavelength at which maximum radiant energy occurs is (a) 2.87 µm (b) 1.63 µm (c) 1.01 µm (d) 20.85 µm 

asked May 25, 2018 in Physics
1 answer 5 views

The transferred electron bulk effect occurs in

answered May 23, 2018 in Physics
1 answer 9 views

A compact microstrip antenna may be obtained by

answered May 23, 2018 in Physics
1 answer 95 views

Frequency is inherently a physical quantity with characteristics.  a. Positive b. negative c. both a &b d. none of above 

answered May 17, 2018 in Physics
1 answer 7 views

The degree of coupling depends  (A) size of hole (B) location of holes (C) size and location of holes (D) not depend on size or location of hole

answered May 17, 2018 in Physics
1 answer 12 views

Form the hot metal surface electrons escape because   (A) of change of state from metal to gas due to heat. (B) of change of state from gas to metal (C) the energy supplied is greater than the work function (D) the energy is greater than Fermi level

answered May 17, 2018 in Physics
1 answer 17 views

In any atom the potential energy of an orbiting electron is   (A) always positive (B) always negative (C) sometime positive, sometime negative (D) numerically less then its kinetic energy.

answered May 16, 2018 in Physics
1 answer 13 views

At a particular temperature and current density, the critical magnetic field for a Type I superconductor is Bc and that for a type II superconductor ranges from Bc1 to Bc2 keeping other parameters unloaded. both superconductors are now subjected to a magnetic field B that satisfies the conditions B>Bc and Bc1 < ... will maintain a vortex state  (d) Type I superconductor will switch to the normal conducting state, while Type II superconductor will maintain a vortex sate

answered May 15, 2018 in Physics
1 answer 18 views

In order to generate electron-hole pairs, the maximum wavelength of radiation for Silicon (Band gap = 1.1 eV) is  (a) 1.88 μm (b) 1.68 μm (c) 1.13 μm (d) 1.54 μm

answered May 15, 2018 in Physics
1 answer 21 views

Silicon dioxide is (A) a conductor (B) an insulator (C) a useful circuit element  (D) useful as contact in MOSFET

answered May 12, 2018 in Physics
1 answer 18 views

A forward-biased PN-junction,  (A) results in increase in diffusion current  (B) results in increase in drift current  (C) results in decrease in drift current  (D) results in decrease in diffusion current

answered May 12, 2018 in Physics
1 answer 15 views

In a PN-junction with open circuit terminal (equilibrium), with P doping higher as compared to N doping (A) N-side depletion region is small as compared to p-side depletion region (B) N-side depletion region is large as compared to p-side depletion region (C) N-side depletion region is same as p-side depletion region (D) Cannot say

answered May 12, 2018 in Physics
1 answer 18 views

Which of the following is true regarding the band-gap energy of a semiconductor ? (A) Minimum energy required to break a covalent bond (B) On breaking of the bond, electron is generated (C) On breaking of the bond, electron-hole pair is generated (D) A & C both are true

answered May 12, 2018 in Physics
1 answer 23 views

The coefficient of reflection for current wave is

answered May 3, 2018 in Physics
1 answer 37 views

The velocity of travelling wave through a cable of relative permittivity 36 is

answered May 3, 2018 in Physics
1 answer 51 views

The average life of neutrons after they decay is

answered May 3, 2018 in Physics
1 answer 55 views

Which of the following statements is not characteristic of a static magnetic field? (A) It is solenoidal. (B) It is conservative. (C) It has no sinks or sources. (D) Flux lines are always closed.

answered Apr 28, 2018 in Physics
1 answer 23 views

At very high temperatures, extrinsic semiconductor becomes intrinsic semiconductor because (A) Of drive in diffusion of dopants & carriers. (B) Band to band transition dominates impurity ionization. (C) Impurity ionization dominates band to band transition. (D) Band to band transition is balanced by impurity ionisation.

answered Apr 28, 2018 in Physics
0 answers 12 views

Tesla is a measure of  (a) magnetic flux density (b) electric flux density (c) magnetic potential (d) electric potential 

asked Apr 9, 2018 in Physics
0 answers 11 views

Angles project true size only when the plane containing the angle and plane of projection are  (a) Aligned (b) Adjacent (c) Perpendicular (d) Parallel

asked Apr 9, 2018 in Physics
0 answers 33 views

X-rays are used for the study of crystal structure because  (a) X-rays are completely absorbed by the crystal (b) the wavelength of X-ray is of the same order of magnitude in the inter-atomic spacing in crystals (c) the wavelength of X-rays is very small in comparison with the inter-atomic spacing in crystals (d) the crystals are completely transparent to X-rays

asked Apr 9, 2018 in Physics
0 answers 30 views

What are the basic laws of physics?

asked Mar 11, 2018 in Physics
0 answers 20 views

What are the basics of physics?

asked Mar 11, 2018 in Physics
0 answers 31 views

Is electricity faster than lightning?

asked Mar 10, 2018 in Physics
0 answers 74 views
1 answer 44 views

What is the charge and mass of an electron?

answered Jan 21, 2018 in Physics
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