The question asks about the electrical conductivity of a semiconductor material at room temperature. We need to understand the basic properties of semiconductors, insulators, and conductors to determine the correct answer.
D) slightly conducting. At room temperature, thermal energy provides enough energy for a small number of electrons to cross the forbidden energy gap from the valence band to the conduction band, making the semiconductor capable of conducting electricity, albeit to a limited extent compared to a good conductor.
The question asks to identify the material with the highest electrical conductivity among the given options. Electrical conductivity is a measure of a material's ability to conduct an electric current. It is the reciprocal of electrical resistivity. Materials with a high number of free electrons typically exhibit high conductivity.
Correct Option: A) Silver has the highest electrical conductivity among the options provided and is, in fact, the best electrical conductor among all metals at room temperature.
This question tests knowledge about how television signals are transmitted and how noise affects different components of these signals. TV broadcasts typically use Amplitude Modulation (AM) for video signals and Frequency Modulation (FM) for audio signals.
Correct Option: D) only the video signals
Electrical disturbances (noise) primarily affect the video signal in TV because video is transmitted using Amplitude Modulation (AM), which is highly susceptible to noise. The audio signal, transmitted using Frequency Modulation (FM), is much more immune to such disturbances.
The question asks about the cause of the characteristic blue luminosity in a mercury arc rectifier. This phenomenon is related to the fundamental principles of gas discharge and atomic excitation.
Correct Option: C) ionization
The blue luminosity is a direct result of the ionization of mercury vapor. When mercury atoms are ionized and then recombine, or when their electrons are excited and de-excite, they emit light at specific wavelengths, which for mercury includes a prominent blue component.
The question asks for the specific stress limit below which a material can withstand repeated stress reversals without failure. This concept is crucial in fatigue analysis of materials.
D) Endurance limit
The endurance limit (also known as the fatigue limit) is the maximum stress amplitude that a material can withstand for an infinite number of load cycles without exhibiting fatigue failure. This is particularly relevant for materials subjected to repeated or cyclic loading, such as those in rotating machinery or vibrating structures, where stress reversal is common. Below this stress level, the material has a very high probability of not failing due to fatigue.
A pycnometer is used to determine
Water content and voids ratio
Specific gravity and dry density
Water content and specific gravity
voids ratio and dry density
The question asks about the primary uses of a pycnometer in soil mechanics. A pycnometer is a specialized flask used for precise measurements related to the density and specific gravity of materials. We need to identify which properties of soil can be determined using this instrument.
C) Water content and specific gravity. As explained above, a pycnometer is a standard apparatus used in laboratories for determining both the specific gravity of soil solids and the water content of soil samples.
The question asks for the maximum permissible shear stress for M20 grade concrete. This value is specified by Indian Standard (IS) codes for reinforced concrete design (IS 456:2000). The maximum shear stress, denoted as \(\tau_{c,max}\), depends on the grade of concrete.
Correct Option: C) 2.8 N/mm²
The maximum shear stress for M20 grade concrete, as per IS 456:2000 (Table 20), is \(2.8 \text{ N/mm}^2\). This is a limiting value to prevent shear failure of the concrete section, even when shear reinforcement is provided.
Lacings are structural elements used in built-up columns to connect individual components (like angles or channels) and make them act as a single unit. The primary function of lacings is to resist the shear force developed in the column due to axial compression and to hold the main members at a specified distance. For design purposes, it is assumed that lacings primarily carry axial forces (tension or compression) along their length.
Correct Option: D) Axial loading only
Lacings are designed to carry axial forces (tension or compression) resulting from the shear force in the main column. They are treated as truss members.
The question asks about the primary factor determining the flow profile of a fluid. The flow profile refers to how the velocity of a fluid changes across a cross-section of the flow. This is fundamentally determined by whether the flow is laminar or turbulent, which is characterized by a dimensionless number.
Correct Option: C) The Reynolds number. The Reynolds number is a dimensionless quantity that predicts the flow regime (laminar or turbulent), which in turn dictates the velocity profile of the fluid. It incorporates fluid properties (density, viscosity), flow velocity, and characteristic dimension (like pipe diameter).
The question asks for the definition of an "event" in the context of PERT (Program Evaluation and Review Technique) analysis. PERT is a project management tool used to schedule, organize, and coordinate tasks within a project. Understanding the basic terminology of PERT, specifically what constitutes an event, is crucial.
Correct Option: A) Start or finish of a task