In this chapter, we will learn about basic concepts of electric circuits, or we can say this chapter is all about introduction to electric circuits.
In electric circuits, there are two fundamental theories namely,
- Circuit Theory
- Electromagnetic Theory (EM Theory)
In electrical engineering, we generally study how to communicate signals or transfer energy from one point to another.
Electric Circuit
An electric circuit is nothing but an interconnection of various electrical or electronic components such as batteries, switches, lamps, etc.
We use electric circuits in a huge number of applications to accomplish various tasks or functions.
The following figure shows a typical simplest form of electric circuit consisting of electrical components namely, DC voltage source, a resistor, and a lamp.
Analysis of Electric Circuit
The process of studying the behavior of an electric circuit is referred to as the analysis of electric circuit.
During analysis of electric circuit, we try to answer the following questions –
- How does the electric circuit respond to an applied input?
- How do the components or devices in the circuit interact with each other?
System of Units
In electrical engineering, we use an international measurement language, which is the International System of Units (also known as SI System of Units). This measurement system was adopted by the General Conference on Weights and Measures in the year 1960.
The SI system of units has seven (7) base units of measurement, which are given in the following table –
|
S. No. |
Physical Quantity | SI Unit |
|
1 |
Length (l) |
Meter (m) |
|
2 |
Mass (m) |
Kilogram (kg) |
|
3 |
Time (t) |
Second (s) |
|
4 |
Electric Current (I) |
Ampere (A) |
|
5 |
Thermodynamic Temperature (T) |
Kelvin (K) |
|
6 |
Luminous Intensity |
Candela (cd) |
| 7 |
Charge (Q)* |
Coulomb (C) |
* SI unit of charge is the derived unit.
SI Prefixes
Prefixes are keywords attached to SI measurement units to represent very large and very small values of physical quantities. The following table provides various SI prefixes used in electrical and electronics engineering –
|
SI Prefix |
Multiplier |
|
Exa (E) |
1018 |
|
Peta (P) |
1015 |
|
Tera (T) |
1012 |
|
Giga (G) |
109 |
|
Mega (M) |
106 |
|
kilo (k) |
103 |
|
hecto (h) |
102 |
|
deka (da) |
10 |
|
deci (d) |
10-1 |
|
centi (c) |
10-2 |
|
milli (m) |
10-3 |
|
micro (µ) |
10-6 |
|
nano (n) |
10-9 |
|
pico (p) |
10-12 |
|
femto (f) |
10-15 |
|
atto (a) |
10-18 |