Course: From Basic Science to Web Hosting
Module 01 — Basic Science
What Is Electric Charge?
Difficulty: Beginner
Prerequisites: Lesson 003 — What Is an Electron?
Estimated time: 15–20 minutes
1. Learning Objectives
After this lesson, you should understand:
- What electric charge is
- Positive and negative charge
- Why charges attract and repel
- What a Coulomb is
- What electric force is
- What an electric field is
- How charge leads toward voltage and current
2. Start With the Electron
From Lesson 003:
Electron
↓
Negative electric chargeThe electron isn’t “made of charge” in the ordinary sense.
Rather, electric charge is an intrinsic property of the electron.
Similarly, a proton has positive electric charge.
3. What Is Electric Charge?
Electric charge is a fundamental physical property that determines how matter participates in electromagnetic interactions.
We commonly describe charge using two signs:
Positive (+)
Negative (−)For example:
Proton → +
Electron → −
Neutron → 0 net charge4. Why Do We Have Positive and Negative?
The signs are labels for two opposite types of electric charge.
The important experimental rule is:
Like charges repel
Unlike charges attractTherefore:
+ ←→ + repel
− ←→ − repel
+ ←→ − attract5. Electric Charge Is Quantized
Electric charge comes in discrete amounts.
The magnitude of the elementary charge is approximately:
e = 1.602 × 10⁻¹⁹ CAn electron has:
−eA proton has:
+eThe unit used to measure electric charge is the Coulomb (C).
6. What Is a Coulomb?
A Coulomb is a unit of electric charge.
One Coulomb is a very large amount compared with the charge of one electron.
Approximately:
1 C ≈ 6.24 × 10¹⁸ elementary chargesSo a tiny electron charge becomes a large quantity when billions of billions of charges are considered together.
7. Charge Can Exist on Objects
An object doesn’t have to be an individual particle to have a net electric charge.
Suppose an object has:
More electrons than protonsIt has a net:
Negative chargeIf it has fewer electrons than would balance the positive charge of its nuclei:
Positive net charge8. Example: Static Electricity
Rub a balloon against certain materials.
Electrons can transfer between surfaces.
The result can be:
Balloon
↓
Net electric charge
↓
Attraction to another objectThis is one familiar example of electrostatic phenomena.
9. Electric Force
Charged objects exert electromagnetic forces on each other.
For two point charges, the magnitude of the electrostatic force is described by Coulomb’s law:
F = k |q₁q₂| / r²where:
F = force
q₁ = first charge
q₂ = second charge
r = separation distance
k = Coulomb constantThe important relationships are:
More charge
↓
Stronger forceand:
Greater distance
↓
Weaker forcewith an inverse-square relationship for ideal point charges.
10. Why Does Distance Matter?
Imagine two charges close together:
+ −They interact strongly.
Move them farther apart:
+ −The force becomes weaker.
Mathematically:
F ∝ 1/r²So if distance doubles:
Force becomes 1/4for the idealized point-charge case.
11. Electric Field
Instead of thinking only:
“Charge A pushes charge B.”
Physics uses the concept of an electric field.
A charge creates an electric field in the surrounding space.
Conceptually:
Charge
↓
Electric field
↓
Force on another chargeThis is a very important idea for understanding electronics.
12. Field vs Force
These are related but different.
Electric field
Describes the force per unit positive test charge at a location.
E = F/qElectric force
The force experienced by a particular charge.
F = qESo:
Electric field
↓
Acts on charge
↓
Electric force13. Electric Field Around a Positive Charge
A simplified diagram:
↑
↗ │ ↖
/ │ \
← + →
\ │ /
↘ │ ↙
↓Electric-field lines point away from a positive charge.
For a negative charge, they point toward it:
↓
↙ │ ↘
/ │ \
→ − ←
\ │ /
↖ │ ↗
↑These lines are visualization tools, not physical objects.
14. Electric Potential
Now we introduce another important concept.
Electric potential describes electric potential energy per unit charge.
V = U/qwhere:
V = electric potential
U = electric potential energy
q = chargeElectric potential is measured in:
Volts (V)15. Voltage
Voltage is a difference in electric potential between two points.
For example:
Point A = 5 V
Point B = 0 V
Voltage difference = 5 VThis is why a battery can provide a voltage between its terminals.
16. Voltage Is Not Charge
These concepts must not be confused.
Charge
↓
Measured in Coulombs
Voltage
↓
Potential difference
↓
Measured in Volts17. Voltage Is Not Current
Again:
Voltage
↓
Potential difference
Current
↓
Rate of charge flowThey are related, but they are different physical quantities.
18. Battery
A battery uses chemical processes to maintain a potential difference between its terminals.
Conceptually:
Chemical energy
↓
Charge separation / electrochemical processes
↓
Potential difference
↓
Voltage
↓
Can drive current through a circuitA battery doesn’t simply “contain voltage.”
It maintains an electrical potential difference through electrochemical processes.
19. Closing the Circuit
Consider:
Battery
│
│
└──── Load ────┐
│
└──── BatteryWhen the circuit is complete, an electric field is established throughout the conducting path and charge carriers respond, producing current.
Conceptually:
Battery
↓
Potential difference
↓
Electric field
↓
Charge-carrier motion
↓
Current20. Current
Current measures charge flow rate:
I = ΔQ/ΔtThe unit is:
Ampere (A)One ampere corresponds to one Coulomb of charge passing a point per second.
1 A = 1 C/s21. Charge → Field → Voltage → Current
You can now see the relationships:
Electric charge
↓
Electric field
↓
Electric potential
↓
Potential difference
↓
Voltage
↓
Electric field in circuit
↓
Charge-carrier motion
↓
CurrentThese are foundational ideas in electronics.
22. From Physics to a Computer
Now connect this lesson to your eventual goal.
Electric charge
↓
Electric field
↓
Voltage
↓
Current
↓
Electronic circuit
↓
Semiconductor
↓
Transistor
↓
Logic gate
↓
Digital circuit
↓
CPUThen:
CPU
↓
Computer
↓
Operating System
↓
Network
↓
Internet
↓
Web Server
↓
Web Hosting23. Important Scientific Idea
The electron itself does not travel through a wire from your computer in Thiruvananthapuram all the way to a remote web server.
Communication involves electromagnetic fields and physical signals propagating through the communication medium, while charge carriers in the conductors respond locally.
This distinction becomes especially important when you later study:
- Transmission lines
- Ethernet
- Fiber optics
- Radio
- Wi-Fi
- Network signaling
24. Three Things to Remember
Charge
Property of particles/matterElectric field
Describes electromagnetic influence in spaceVoltage
Difference in electric potentialThen:
Voltage + suitable circuit
↓
Electric field
↓
Current25. Quick Check
1. What charge does an electron have?
Negative.
2. What charge does a proton have?
Positive.
3. What happens between like charges?
They repel.
4. What happens between opposite charges?
They attract.
5. What is the unit of charge?
Coulomb (C).
6. What is the unit of voltage?
Volt (V).
7. What is the unit of current?
Ampere (A).
8. What is the relationship between current and charge?
I = ΔQ/ΔtConnection to the Next Lesson
We now have:
Matter
↓
Atom
↓
Electron
↓
Electric charge
↓
Electric field
↓
Voltage
↓
CurrentThe next question is:
How do voltage and current behave inside an actual circuit?
Lesson 005 — What Is an Electrical Circuit?
We will study:
Circuit
↓
Source
↓
Conductors
↓
Load
↓
Open circuit
↓
Closed circuit
↓
Voltage
↓
Current
↓
Resistance
↓
Ohm's LawThat will take us from basic physics into actual electrical engineering, which is the next major step toward understanding transistors and computers.
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