Chapter 2 : Basics of Electricity
Topics covered in this snack-sized chapter:
Coulomb’s Law states that:
The magnitude of the Electrostatic force of interaction between two point charges is:
- Directly proportional to the scalar multiplication of the magnitude of charges and,
- Inversely proportional to the square of the distance between them.
The electric force F acting on a point charge Q1
as a result of the presence of a second point charge Q2
is given by:
Here, k is Coulomb’s Constant
Ohm’s Law states that, “The resistance of a conductor is equal to ratio of voltage over current”.
It can also be presented as:
“When electrical potential (voltage) creates a flow of electricity (current), the current and the electrical resistance of
the circuit are proportional to the voltage.”
Here,
“The flux of electric field through a closed surface is proportional to the charge enclosed”.
Electric Flux is the amount of electric field passing through a closed surface.
- Flux is positive when electric field is outward, and
- Negative when electric field is inward (through the closed surface).
An Electrical Source is a voltage or current generator capable of supplying energy to a circuit.
Electrical sources, in practice, include things like:
- The ever-present wall plug
An ideal voltage source is a circuit element where the voltage across the source is independent of the current through it.
- The internal resistance of an ideal voltage source is zero.
Ideal Independent Voltage Source:
An ideal independent
voltage source is characterized by having a constant voltage across its terminals, regardless of the load connected to the terminals.
The ideal voltage source can supply any amount of current.
- Furthermore, the ideal independent voltage source can supply any amount of power.
Dependent Voltage Source:
A dependent voltage source is characterized by depending on a voltage or current somewhere else in the circuit.
- The symbol for the voltage source is shown below:
A circuit containing a dependent voltage source is shown below:
An ideal current source is a circuit element where the current through the source is independent of the voltage across it.
- The internal resistance of an ideal current source is infinite.
Ideal Independent Current Source:
An ideal independent current source is characterized by providing a constant value of current, regardless of the load.
- If the current source is truly ideal, it can provide any value of voltage and any amount of power.
Dependent Current Source:
A dependent current source is characterized by depending on a voltage or current somewhere else in the circuit.
A circuit containing a dependent current source is shown below:
- A circuit with a voltage controlled dependent current source.
