Materials Science and Applied Physics Questions and Answers
Electrical Conductivity: Metals vs. Plastics
Why is the electrical conductivity of metals very high while that of plastics is very low?
Metals: Metallic bonding leaves valence electrons delocalised as an “electron sea” (about 1028–1029 electrons/m3). In band theory, the conduction band is partly filled or overlaps the valence band, so there is no energy gap. Electrons move freely under a small field. Conductivity is approximately 106–108 S/m.
Plastics: Atoms are held by strong covalent bonds,
Read MoreEngineering Materials: Properties, Structures, and Processing
1. Classification of Engineering Materials
Engineering materials are classified based on their atomic bonding and physical properties:
- Metals and Alloys: Characterized by metallic bonding, high electrical/thermal conductivity, ductility, and strength. Examples: Iron (Fe), Copper (Cu), Steel (Fe-C), Brass (Cu-Zn).
- Ceramics: Inorganic, non-metallic solids. High hardness, brittle, and excellent insulators. Examples: Alumina (Al₂O₃), Silicon Carbide (SiC).
- Polymers: Organic compounds with long-chain
Essential Workshop Tools and Metalworking Techniques
1. Types of Chisels in Fitting Work
Chisels are cutting tools used in fitting work to remove excess metal and shape workpieces. They are typically made of high-carbon steel and used with a hammer.
- Flat Chisel: Used for general cutting and smoothing surfaces.
- Cross-cut Chisel: Used for cutting grooves and keyways.
- Round Nose Chisel: Used for making semicircular grooves.
- Diamond Point Chisel: Used for making V-shaped grooves and sharp corners.
2. Bench Vice, V-Block, and Surface Plate
These essential workshop
Read MoreMeasuring Waveform Voltage and Frequency with a CRO
Experiment 1: Waveform Measurement
Aim: To measure the voltages and frequency of different waveforms using a Cathode Ray Oscilloscope (CRO).
Apparatus: Cathode Ray Oscilloscope (CRO), function generator, BNC connector, and connecting wires.
Theoretical Background
Cathode Ray Oscilloscope (CRO)
The Cathode Ray Oscilloscope (CRO) is a common laboratory instrument that provides accurate time and amplitude measurements of voltage signals over a wide range of frequencies. Its reliability, stability, and ease
Read MoreInternal leakage in
8 Explain the working principle of Ultrasonic Testing (UT). Describe the differences between The Pulse-Echo Method and the Transmission Method in UT.
Working Principle of Ultrasonic Testing (UT)
The fundamental principle of UT involves the use of high-frequency sound waves (ultrasonic vibrations) to probe the internal structure of a material.
Generation:
A pulser sends high-voltage electrical pulses to a transducer.
Conversion:
The transducer, containing piezoelectric crystals, converts this electrical
Essential Metrology and Measurement Systems Explained
1. Instruments for Angular Measurement
The following four instruments are commonly used for angular measurement:
- Bevel Protractor: Used for measuring angles between two surfaces with a vernier scale.
- Sine Bar: Used in conjunction with slip gauges to measure angles accurately based on trigonometry.
- Angle Gauges: Hardened steel blocks of precise angles used as reference standards.
- Clinometer: A specialized version of a spirit level used for measuring angles of inclination or slope.