Electrical Instrumentation and Measurement Principles
Strain Measurement with Strain Gauges
A strain gauge is a resistive transducer that changes its electrical resistance in proportion to the mechanical strain applied to it.
Principle and Gauge Factor
When a conductor is stretched, its length increases and diameter decreases, both of which increase resistance (R = ρL/A). The Gauge Factor (GF) is defined as: GF = (∆R/R) / (∆L/L) = (∆R/R) / ε, where ε is strain. For metallic gauges, GF ≈ 2; for semiconductor gauges, GF = 100–150.
Wheatstone
Read MoreHidden Surface Elimination and CRT Display Technology
When rendering a 3D scene onto a 2D screen, objects closer to the camera must obscure objects that are behind them. Identifying and removing parts of a scene that are blocked from view is called Hidden Surface Elimination (or Visible Surface Detection).
These techniques are divided into two categories: Object-Space methods (which analyze physical geometry in 3D coordinates) and Image-Space methods (which work pixel-by-pixel in 2D screen coordinates).
1. Back-Face Removal (Object-Space)
Back-face removal
Read MoreElectrical Power Systems: Circuit Breakers and Machines
Transient Phenomena in Power Lines
A1. Transient Switching Phenomena
When an inductive power line is switched on, the steady-state sinusoidal current is not reached immediately. Since current through an inductance cannot change instantaneously, a transient DC component appears if the switching instant does not match the steady-state initial value. The current is defined as i(t) = i_st(t) + i_tr(t). The worst case occurs in highly inductive circuits when energization happens near voltage zero.
A2. Transient
Read MoreVector Calculus and Electromagnetic Field Principles
Gauss Divergence Theorem
The total outward flux of a vector field through a closed surface is equal to the volume integral of the divergence of the vector field over the region enclosed by the surface.
Where: A = vector field, S = closed surface, V = volume enclosed by surface, dS = differential surface element, ∇ ⋅ A = divergence of vector field.
Limitations
- Applicable only for closed surfaces.
- Vector field must be continuous and differentiable.
Applications
- Gauss Law in Electrostatics
- Fluid flow and
Linear Circuit Theorems and Network Analysis
Superposition Theorem
… Superposition Theorem: In a linear circuit with multiple sources, the response (voltage or current) in any element is equal to the algebraic sum of the responses caused by each source acting alone.
Procedure
- Consider one source at a time.
- Replace other sources:
- Voltage source → short circuit
- Current source → open circuit
- Find the response due to each source.
- Add all responses algebraically.
Important Note: Power cannot be directly calculated using superposition.
Limitations
- Only
Essential Electrical Engineering Concepts Summary
Unit 1: Basic Electrical Principles
1. Ohm’s Law
At constant temperature, current is directly proportional to voltage; V = IR.
2. Kirchhoff’s Laws
- KCL: Algebraic sum of currents at a node is zero.
- KVL: Sum of voltages in a loop is zero.
3. Resistance, Inductance, Capacitance
- Resistance (Ohm): Opposes current flow.
- Inductance (Henry): Opposes current change.
- Capacitance (Farad): Stores electric charge.
4. Active and Passive Elements
- Active: Voltage sources, current sources.
- Passive: Resistor, inductor, capacitor.