Physics - Study Mode
[#981] The substance which conducts current in the solid state is
Correct Answer
(B) Graphite
Explanation
Solution: One free electron is there due to which graphite conducts electricity in the solid state.
[#982] Electric current is measured by which instrument?
Correct Answer
(B) Ammeter
Explanation
Solution: The electric current in one part of a circuit is measured with an ammeter, which gives a reading in ampere.
[#983] The wavelength at which the peak of intensity of blackbody radiation occurs
Correct Answer
(B) Decreases with increase in temperature
Explanation
Solution: According to Wien’s displacement law, when the temperature of a blackbody radiator increases, the overall radiated energy increases. Wavelength of maximum emission from a blackbody is inversely proportional to its temperature. Shorter-wavelength (higher-frequency) light corresponds to higher-energy photons.
[#984] Which of the following principle is used to produce ''low-temperatures' ?
Correct Answer
(D) Adiabatic demagnetisation
Explanation
Solution: Magnetic refrigeration is a cooling technology based on the magneto-caloric effect. This technique can be used to attain extremely low temperatures, as well as the ranges used in common refrigerators, depending on the design of the system. The magnetocaloric effect (MCE, from magnet and calorie) is a magneto-thermodynamic phenomenon in which a change in temperature of a suitable material is caused by exposing the material to a changing magnetic field. This is also known by low temperature physicists as adiabatic demagnetization, due to the application of the process specifically to create a temperature drop
[#985] The first law of thermodynamics is simply the case of
Correct Answer
(D) The law of conservation of energy
Explanation
Solution: The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed.