Description : First super conductor was discovered by a) Kelvin b) Hertz c)Einstein d) Kamerlingh Ornes
Last Answer : d) Kamerlingh Ornes
Description : Substances of conductivity between 10–10 10–20 (n m )–1 are: a) Insulators b) Semiconductors c)Super conductors d)Good conductors
Last Answer : a) Insulators
Description : he substances of conductivity of the order of 10–6 – 10–4 (m)–1 are : a) Insulators b) Super conductors c) Semiconductors d)Good conductors
Last Answer : d)Good conductors
Description : The fractional change in resistance per kelvin is known as, a. temperature coefficient of resistance b. coefficient of Voltage of charge c. thermal expansion d. all of above
Last Answer : a. temperature coefficient of resistance
Description : Which of the following principle is used to produce low-temperatures'? (1) Super conductivity (2) Joule-Kelvin effect (3) Thermo-electric effect (4) Adiabatic demagnetization
Last Answer : (4) Adiabatic demagnetization Explanation: Magnetic refrigeration is a cooling technology based on the magnetocaloiic effect. This technique can be used to attain extremely low temperatures, as well as the ... of a suitable material is caused by exposing the material to a changing magnetic field.
Description : Which of the following principle is used to produce ‘low-temperatures’ ? (1) Super conductivity (2) Joule-Kelvin effect (3) Thermo-electric effect (4) Adiabatic demagneti-sation
Last Answer : Adiabatic demagneti-sation
Description : Conductivity of semi conductor is increased by: a) Decrease of temperature b) By keeping temperature constant c) Increase of temperature d) none of above
Last Answer : d) none of above
Description : Good conductors have conductivity of the order of a) 10–10 (m)–1 b) 10–7 (m)–1 c) 10 7 (m)–1 d) 10–9 (m)–1
Last Answer : c) 10 7 (m)–1
Description : Which of the following has the lowest electrical conductivity? A) Mercury B) Silver C) Copper D) Gold
Last Answer : Which of the following has the lowest electrical conductivity? A) Mercury B) Silver C) Copper D) Gold
Description : Absolute temperature in Kelvin. A. ˚C +273 B. ˚C+75 C. ˚C+19 D. ˚C +290
Last Answer : A. ˚C +273
Description : _______ codified the first two laws of thermodynamics and deducedthat the absolute zero of temperature is 273.15° C. she was honouredfor this with the naming of the Kelvin temperature scale.
Last Answer : William Thomson
Description : A temperature scale whose zero point is absolute zero, the temperature of “0” entropy at which all molecular motion stops. a. Celsius b. Fahrenheit c. Kelvin d. Rankine
Last Answer : Kelvin
Description : What temperature scale is identical to the Kelvin scale? A. Ideal gas temperature scale B. Ideal temperature scale C. Absolute gas temperature scale D. Triple point temperature scale
Last Answer : Ideal gas temperature scale
Description : The unit of absolute permittivity of a medium is
Last Answer : Farad/ metre
Description : Tick the wrong statement. a) Velocity of light is independent of the motion of the observer. b) Velocity of light in free space is the same in all directions. c) Velocity of light in free space is different in different directions. d) Absolute motion or absolute rest is meaningless to talk about
Last Answer : c) Velocity of light in free space is different in different directions
Description : The potential difference set up across the depletion region is called (a) Absolute potential (b) neutral potential (c) reverse potential (d) potential barrier
Last Answer : (d) potential barrier
Description : The resistance of a conductor at absolute zero (OK) is a. zero almost b. infinite almost c. May increase or decrease d. None
Last Answer : zero almost
Description : Arange ofmicrowave frequenciesmore easilypassed bythe atmospherethan are theothersis called a a.window b. critical frequency c. gyro frequency range d. resonance in the atmosphere
Last Answer : a.window
Description : Distancesnearthe skip distance should beused forthe sky-wave propagation a. to avoid tilting b.topreventsky-wave andupper rayinterference c. to avoid the Faraday effect d. so as nor to exceed the critical frequency
Last Answer : b.topreventsky-wave andupper rayinterference
Description : The minimum frequency required to eject electrons from a metallic surface is called a) Critical frequency b) Peak value of frequency c) Threshold frequency d)Photo frequency
Last Answer : c) Threshold frequency
Description : The critical radius of insulation for a spherical shell is (where, K = thermal conductivity of insulating material h0 = heat transfer coefficient at the outer surface) (A) K/h0 (B) 2K/h0 (C) h0 /K (D) h0 /2K
Last Answer : (B) 2K/h0
Description : What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively. (A) 2 (B) 8 (C) 10 (D) 40
Last Answer : (A) 2
Description : The ratio of thermal & electrical conductivity is same for all the metals at the same temperature; and at around room temperature, this ratio is proportional to(where, T = absolute temperature, °K) (A) T (B) 1/T (C) T2 (D) 1/T2
Last Answer : A) T
Description : Property of material which allows it to be drawn out into wires is (A) Ductility. (B) Solder ability. (C) Super conductivity. (D) Malleability.
Last Answer : (A) Ductility.
Description : Superconductors are those elements – (1) Whose conductivity is intermediate between metals and insulators (2) Whose resistance falls almost to zero at very low temperature (3) Which conduct electricity only at super-high temperature (4) Which conduct electricity only, at super-high temperatures
Last Answer : (2) Whose resistance falls almost to zero at very low temperature Explanation: Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in ... lines from the interior of the superconductor as it transitions into the superconducting state.
Description : The temperature at which the catalytic activity of the catalyst is maximum, is called (1) room temperature (2) critical temperature (3) absolute temperature (4) optimum temperature
Last Answer : d) optimum temperature
Description : Critical compressibility factor for all substances (A) Are more or less constant (vary from 0.2 to 0.3) (B) Vary as square of the absolute temperature (C) Vary as square of the absolute pressure (D) None of these
Last Answer : (A) Are more or less constant (vary from 0.2 to 0.3)
Description : Indicate which of the following material does not retain magnetism permanently. (a) Soft iron (b) Stainless steel (e) Hardened steel (d) None of the above
Last Answer : (a) Soft iron
Description : A material which is slightly repelled by a magnetic field is known as (a) ferromagnetic material (b) diamagnetic material (c) paramagnetic material (d) conducting material
Last Answer : (b) diamagnetic material
Description : Thevelocityfactor of a transmissionline a. depends on the dielectric constant of the material used b. increases the velocity along the transmission line c. is govern by the skin effect d. is higher for a solid dielectric than for air
Last Answer : a. depends on the dielectric constant of the material used
Description : The X-rays emitted in inner shell transitions are called _____ as their energy depends upon the type of target material. a) gamma rays b) special X-rays c) Characteristic X-rays d) continuous X-rays
Last Answer : c) Characteristic X-rays
Description : If a material object moves with the speed of light ‘c’ its mass becomes a) equal to its rest mass b) Four times of its rest mass c) Double of its rest mass d) Infinite
Last Answer : d) Infinite
Description : Which one of the following waves requires a material medium for their propagation? a) Light waves b) X– rays c) -rays d) Sound waves
Last Answer : d) Sound waves
Description : The mutual inductance of the coil depends upon: a. density of the coil b. stiffness of coil c. material of coil d. geometry of the coil
Last Answer : d. geometry of the coil
Description : Specific resistance of a wire a. will depend on its length b. will depend on its radius c. will depend on the type of material of the wire d. will depend on none of the above
Last Answer : c. will depend on the type of material of the wire
Description : Which one is the best material for making connecting wires? a. Iron b. Tungsten c. Silver d. Copper
Last Answer : d. Copper
Description : Assertion (A): Micelles are formed by surfactant molecules above the critical micellization concentration `(CMC)` . Reason(R): The conductivity of a s
Last Answer : Assertion (A): Micelles are formed by surfactant molecules above the critical micellization concentration ` ... If both Assertion & Reason are False.
Description : For organic compounds, group contribution method can be used for the estimation of (A) Critical properties (B) Specific gravity (C) Specific volume (D) Thermal conductivity
Last Answer : (A) Critical properties
Description : How is the cold room temperature maintained?
Last Answer : The cold room has temperature switch (thermostat) which has a cut-in and cut-off temperature setting. Depending on the setting, the compressor cuts when the temperature rises and cuts-off when the temperature cools down to the set value.
Description : What happens to resistance of conductors when temperature rises?
Last Answer : For conductors an increase in temperature will cause their resistance to increase.
Description : What happens to insulation when temperature rises?
Last Answer : For insulators, an increase in temperature will cause their resistance to decrease -which is why excessive temperature is often the main reason why insulation fails
Description : In order to obtain spectrum from the emitted radiation, the atomic gas or vapour must be excited at a) much less than atmospheric pressure b) much high than atmospheric pressure c) atmospheric pressure d) high pressure and temperature
Last Answer : a) much less than atmospheric pressure
Description : Silicon transistors are preferred because: (a) High operating temperature (b) Low leakage current (c) Suited to high frequency circuits (d) All
Last Answer : (d) All
Description : Depletion region of a junction is formed _________ (a) during the manufacturing process (b) under forward bias (c) under reverse bias (d) when temperature varies
Last Answer : (a) during the manufacturing process
Description : Thermistor with high negative temperature coefficient are very accurate for measuring low temperature especially near is a. 10 K b. 70K c. 200K d. 35K
Last Answer : c. 200K
Description : Resistance of a wire on increasing its temperature will a. increase with rise in temperature b. decrease with rise in temperature c. will remain same d. depends upon altitude of experimentation
Last Answer : a. increase with rise in temperature
Last Answer : To limit the operating temperature an electrical machine should have proper current rating.
Description : Ultra-super critical boiler uses steam with very high temperature up to …… a) 980° b) 620° c) 550° d) 720°
Last Answer : b) 620°
Description : If the thermal conductivity of a wall material is independent of temperature, the steady state temperature distribution in the very large thin plane wall having steady, uniform surface temperature follows __________ ... (A) Hyperbolic (B) Parabolic (C) Linear (D) Logarithmic
Last Answer : (C) Linear
Description : Thermal conductivity of a conducting solid material depends upon its (A) Temperature (B) Porosity (C) Both (A) & (B) (D) Neither (A) nor (B)
Last Answer : (C) Both (A) & (B)