Electric Current and Circuits

Electric Current and Circuits

• Electric current is the flow of electrons through a conductor.
• An electric circuit is a continuous path for current flow between a cell's terminals.
• Current flows from the positive to the negative terminal of a cell.
• Basic circuit components include a cell, bulb, connecting wires, and a switch.

Circuit Diagrams

• Circuit diagrams use symbols to represent components.

Closed vs. Open Circuits

• A closed circuit allows continuous current flow; the switch is "ON".
• An open circuit has interrupted current flow; the switch is "OFF".

Heating Effect of Electricity

• Electric energy is converted to heat energy when current flows through a conductor.
• Heat produced depends on wire length, thickness, and material.
• This effect is used in devices like irons, heaters, kettles, dryers, and hotplates.

Circuit Components

• Element: A coil of wire that gets red hot producing heat, made of Nichrome.
• Filament: A thin wire that glows producing light, made of tungsten.

Efficient Lighting Sources

• CFLs (Compact Fluorescent Lamps) and LEDs (Light Emitting Diodes) use significantly less electricity than traditional bulbs for the same light output.
• CFLs contain mercury (toxic).
• LEDs are more energy-efficient than other options.

Electric Fuses

• Fuses are safety devices in circuits preventing damage from excess current.
• They contain a material that quickly melts and interrupts the circuit if current exceeds a safe limit, preventing fires.

Excess Current Causes

• Overloading: Too many devices on a single circuit can draw too much current.
• Short Circuit: Damaged insulation allowing wires to touch, increasing current flow.

Miniature Circuit Breakers (MCBs)

• MCBs automatically switch off when current exceeds a safe level, unlike fuses which melt.
• MCBs are easily reset/turned back on.
• MCBs are safer and more convenient than fuses.

Magnetic Effect of Electricity

• When an electric current flows through a conductor, a magnetic field forms around it.
• Hans Christian Oersted discovered this effect.
• An experiment using a compass and wire demonstrates this effect.

Electromagnets

• An electromagnet is a current-carrying coil of wire wrapped around an iron core.
• Electromagnets create a strong magnetic field when current flows through the coil.
• They can be used in various applications including lifting heavy objects.
• Electromagnets are used in separating magnetic materials, treating injuries, electric bells, and toys.

Electric Bells

• Electric bells use the magnetic effect of electricity.
• A key component is an electromagnet.
• The electromagnet's magnetism causes a hammer to strike a gong, producing sound.
• They use the principle of a circuit breaking and reconnecting to make the hammer move.