What is Voltage?
Voltage is the electrical force that pushes electric charges through a circuit. Without voltage, electrons would remain stationary and no electric current would flow. Every electrical and electronic device requires a voltage source to operate.
What is Voltage?
Voltage is the difference in electrical potential between two points in a circuit.
It represents the amount of energy available to move electric charge from one point to another.
An easy way to think about voltage is as electrical pressure. Just as water pressure pushes water through a pipe, voltage pushes electrons through a wire.
Water Pipe Analogy
A simple water system helps explain voltage.
| Water System | Electrical Circuit |
|---|---|
| Water Pressure | Voltage |
| Water Flow | Current |
| Pipe Restriction | Resistance |
| Water Pump | Battery / Power Supply |
Higher water pressure produces more water flow. Likewise, a higher voltage can produce more current if the resistance remains the same.
How Voltage is Produced
Voltage can be produced in several ways.
- Chemical reactions inside batteries
- Electrical generators
- Solar cells
- Power supplies
- Electromagnetic induction
- Static electricity
All these sources create a difference in electrical potential that causes electrons to move.
The Unit of Voltage
Voltage is measured in volts.
The symbol for voltage is V.
| Unit | Symbol |
|---|---|
| Volt | V |
| Millivolt | mV |
| Kilovolt | kV |
Examples:
- AA battery — 1.5 V
- Car battery — 12 V
- USB power supply — 5 V
- Laptop adapter — 19 V
- Household mains — typically 120 V or 230 V AC depending on the country
Direct Voltage (DC)
Direct voltage keeps the same polarity all the time.
Examples include:
- Batteries
- Power banks
- USB chargers
- Solar panels
- Most electronic circuits
Alternating Voltage (AC)
Alternating voltage continuously changes polarity.
It alternates between positive and negative values many times every second.
Examples include:
- Household mains electricity
- Generators
- Electrical distribution systems
Measuring Voltage
Voltage is measured using a voltmeter or a digital multimeter (DMM).
Unlike an ammeter, a voltmeter is connected in parallel with the component being tested.
Good voltmeters have very high internal resistance so that they draw very little current from the circuit.
Voltage in Electronic Circuits
Different electronic components require different operating voltages.
| Component | Typical Voltage |
|---|---|
| Red LED | ≈ 2 V |
| Blue LED | ≈ 3.2 V |
| Arduino Uno | 5 V |
| ESP32 | 3.3 V |
| Operational Amplifier | ±12 V to ±15 V (typical) |
| Audio Power Amplifier | ±25 V to ±90 V (depending on design) |
Voltage, Current and Resistance
Voltage, current and resistance are closely related.
Increasing the voltage while keeping the resistance constant causes more current to flow.
This relationship is described by Ohm's Law, one of the most important laws in electronics.
Key Points
- Voltage is the electrical force that moves electric charge.
- Voltage is measured in volts (V).
- A battery creates voltage using chemical energy.
- Voltage is measured with a voltmeter connected in parallel.
- Without voltage, electric current cannot flow.
- Voltage is often compared to water pressure in a pipe.