Electric Circuit and Electrical Symbols:
An electric circuit is a closed and continuous path through which electric current flows from the cell, through the components, and back to the cell.
Instead of drawing real objects, scientists use standard electrical symbols to represent circuit components.
Why do we use electrical symbols?
- Universal (same all over the world)
- Easy to draw and understand
- Save time and make circuit diagrams neat
Common Circuit Components:
| Component | Function | Symbol of components |
|---|---|---|
| Electric Cell | Supplies electrical energy |  |
| Battery | Two or more cells connected together |  |
| Bulb (Lamp) | Produces light |  |
| Switch | Controls the flow of current |
  |
| Connecting Wires | Carry electric current |  |
Drawing a Simple Circuit:
Steps to draw a simple circuit:
- Draw the cell/battery symbol.
- Connect components using wire symbols.
- Add the bulb.
- Add the switch.
- Close the switch to complete the circuit.
Current Path:
Battery \(\to\) Wire \(\to\) Bulb \(\to\) Wire \(\to\) Switch \(\to\) Battery
Conductors and Insulators:
Materials are classified based on whether they allow electric current to pass through them.
| Conductors | Insulators |
|
Conductors allow electric current to pass through them because they have free electrons.
Example: Copper
Aluminium
Silver
Gold
Steel
Graphite
|
Insulators do not allow electric current to pass through them.
Example: Plastic
Rubber
Glass
Wood
Paper
Ceramic
|
Why is Copper Used for Electrical Wires?
Although silver is the best conductor, copper is commonly used because it is:
- A very good conductor of electricity.
- Less expensive than silver and gold.
- Easily available.
- Strong and flexible.
Why are wires covered with plastic?
The outer covering is made of plastic or rubber, which are insulators.
Functions of insulation
- Prevents electric shock.
- Prevents short circuits.
- Makes electrical appliances safe to use.
Filament Lamp and LED Lamp:
Filament Lamp:
- Contains a tungsten filament.
- Filament becomes hot and glows.
- Uses more electricity.
- Produces more heat.
- Shorter lifespan.
LED Lamp:
- Contains an LED chip (diode).
- Produces light directly.
- Uses less electricity.
- Produces very little heat.
- Longer lifespan.
Comparison:
| Feature | Filament Lamp | LED Lamp |
|---|---|---|
| Light Production | Heated filament | LED chip |
| Electricity Use | More | Less |
| Heat Produced | High | Low |
| Efficiency | Low | High |
| Lifespan | Short | Long |