1. Symbols of Electric Components

To draw circuit diagrams easily, we use standard symbols:

• Electric Cell: A longer line (positive terminal) and a shorter, thicker line (negative terminal).
• Battery: A combination of two or more cells. The positive terminal of one cell is connected to the negative terminal of the next.
• Switch: Can be in 'ON' position (circuit complete) or 'OFF' position (circuit broken).

2. Heating Effect of Electric Current

• When an electric current flows through a wire, the wire gets hot. This is the heating effect.
• Factors affecting heat: Material (e.g., Nichrome heats up more than Copper), Length, and Thickness of the wire.
• Applications: Electric heaters, geysers, irons, toasters. These contain a coil of wire called an element.
• Safety Devices:
  • Fuse: A safety device that melts and breaks the circuit if excessive current flows, preventing fire and damage.
  • MCB (Miniature Circuit Breaker): Switches that automatically turn off when current exceeds the safe limit.

3. Magnetic Effect of Electric Current

• Discovery: Hans Christian Oersted noticed that a compass needle deflected when placed near a current-carrying wire.
• This proved that a current-carrying wire behaves like a magnet.

4. Electromagnet and Electric Bell

• Electromagnet: A coil of insulated wire wrapped around a piece of soft iron. It acts as a magnet only when current flows through it (Temporary Magnet). Used in cranes, junk yards, and electric bells.
• Electric Bell: Consists of an electromagnet, an armature (soft iron strip), a hammer, and a gong. The circuit breaks and reconnects repeatedly to ring the bell.