56. Circuit Components and Symbols

1. Power and Control

• Cell & Battery: Provide the electrical power to the circuit.

• Switch: Controls the flow of electricity. It must be closed for electricity to flow. An open switch breaks the circuit.

• Fuse: A safety component that "breaks" (melts) if the current flowing through the circuit becomes too high.

2. Light and Direction

• Filament Lamp: A standard small light bulb.

• Diode: Only allows current to flow in one direction.

• LED (Light Emitting Diode): A special diode that emits light when current flows through it in the forward direction. Common in clocks, traffic lights, and modern bulbs.

3. Measuring Devices

• Ammeter: Measures current in Amperes (A). It is always connected in series within the main loop.

• Voltmeter: Measures potential difference (voltage) in Volts (V). It is always connected in parallel across a component.

4. Resistors

Resistors oppose the flow of current. There are four main types to know:

Fixed and Variable Resistors

• Fixed Resistor: Provides a set, unchanging amount of resistance.

• Variable Resistor: Allows you to manually adjust the amount of resistance provided.

LDR (Light Dependent Resistor)

• Function: Resistance changes based on light intensity.

• Behavior: * Bright light: Resistance is low.

  • Darkness: Resistance is high.

• Uses: Automatic night lights and burglar detectors.

Thermistor

• Function: Resistance changes based on temperature.

• Behavior: * Higher temperature: Resistance falls.

  • Lower temperature: Resistance increases.

• Uses: Car engine temperature sensors and electronic thermostats.

5. Summary Table: Special Resistors