The question asks about arc stability in welding processes. Arc stability refers to the consistency and steadiness of the electric arc between the electrode and the workpiece. We need to compare AC and DC welding in terms of arc stability.
B) DC welding provides better arc stability because the current flows in a single direction, maintaining a continuous arc without the periodic extinguishing and reigniting that occurs with AC current.
The question asks about the material used to saturate the porous substance inside an acetylene cylinder. This is a safety measure related to the storage and transportation of acetylene gas.
C) Acetone is the correct answer. Acetylene cylinders are filled with a porous material saturated with acetone to safely store and transport acetylene gas.
The question asks about the primary function of cutting fluid in machining operations. Cutting fluids serve multiple purposes, but one function is generally considered the most critical due to its direct impact on tool life and workpiece quality.
Correct Option: B) Cool the tool and work piece
The most critical function of cutting fluid is to cool the tool and workpiece. This prevents excessive temperature buildup, which can cause rapid tool wear, thermal distortion of the workpiece, and degradation of surface quality.
To answer this question, we need to recall the fundamental construction and purpose of a capacitor. A capacitor is an electronic component designed to store electrical energy in an electric field. Its structure is key to its function.
Correct Option: C) Two conductors separated by a dielectric
The question asks to identify the physical quantity for which 'Electron Volt' is a unit. We need to recall the definition of an electron volt and its relation to fundamental physical quantities.
Correct Option: D) Energy
The question asks about the implication of having no winding resistance in an electrical component, such as a transformer or an inductor. Winding resistance is an inherent property of the conductor used to form the windings. We need to understand the relationship between resistance, current, and power loss.
Correct Option: C) No ohmic power loss
As explained in the step-by-step analysis, if the winding resistance \( R \) is zero, then according to Joule's law \( P = I^2 R \), the ohmic power loss will be zero. This is an ideal condition, as all real windings have some resistance.
The question asks for an alternative name for the short circuit test on a transformer. This test is performed to determine the series parameters of the transformer equivalent circuit, primarily the equivalent impedance, resistance, and leakage reactance.
Correct Option: B) Impedance Test
The question asks about the typical rating range for distribution transformers. Distribution transformers are used to step down the voltage from the primary distribution lines to the voltage levels suitable for end-users (residential, commercial, and light industrial loads). Their ratings are generally smaller compared to power transformers.
D) up to 200 kVA — This range covers a significant portion of distribution transformers used in residential and light commercial applications. While some distribution transformers can be rated higher, "up to 200 kVA" is a very common and appropriate upper limit for the typical distribution transformer.
The frequency of the alternating current (AC) generated by a synchronous generator is directly related to the number of poles in the generator and its rotational speed. This relationship is governed by a fundamental formula in electrical engineering.
The frequency (\(f\)) of a generator is given by the formula:
\[ f = \frac{P \times N}{120} \]where:
Correct Option: A) 50 Hz is the calculated frequency when the generator has 8 poles and rotates at 750 rpm.