Electricity is a fundamental part of our modern lives, powering countless devices and systems. From the massive generation plants like hydroelectric dams that convert the energy of falling water into electrical energy, to the small batteries in our portable gadgets, electricity plays a crucial role.

Electricity generated at power stations reaches our homes and workplaces through a network of wires. We connect appliances to wall sockets to use this power. However, to understand the basics of how electricity works in a simple way, we can explore portable sources like electric cells and batteries.

Important Safety Note: Electricity from wall sockets or generators is dangerous and can cause severe injury or death. Never experiment with household power supply. Always use safe, low-voltage sources like electric cells or batteries (found in torches, clocks, toys, remotes) for experiments.

A Torchlight

A common device that uses a portable source of electricity is a torchlight (or flashlight).

Activity 3.1: Let Us Explore

Observing a torch, you will typically see a lamp (or bulb) and a switch.

Sliding the switch changes the state of the torch. In one position, the lamp lights up, providing illumination. In the other position, the lamp turns off. This demonstrates that the switch controls whether the torch functions or not.

Opening a torch reveals the source of power: typically, two or more electric cells placed inside.

A Simple Electrical Circuit

To understand how the torch works, let's look at its components.

Electric Cell

An electric cell is a self-contained unit that provides electrical energy.

Activity 3.2: Let Us Observe

Every electric cell has two distinct ends or connections called terminals. One is marked with a positive (+) sign and the other with a negative (-) sign.

Physically, the positive terminal is usually represented by a small metal cap that protrudes from one end, while the negative terminal is a flat metal disc at the opposite end.

The electric cell is a convenient, portable source of electrical energy used in many small devices.

Battery

Many devices require more electrical energy than a single cell can provide. A battery is formed by combining two or more electric cells.

Activity 3.3: Let Us Experiment

When multiple cells are used together in a device like a torch, they need to be connected in a specific way to form a battery that provides enough power. The typical connection is in series, where the positive terminal of one cell is connected to the negative terminal of the next cell. Inserting cells in the wrong order or orientation will prevent the device from working.

This series arrangement allows the combined cells to provide energy for a longer time and/or deliver more energy to the circuit.

Interesting Note: Sometimes, even a single cell might be referred to as a "battery," particularly in the context of devices like mobile phones.

Electric Lamp

The component in a torch that produces light is the electric lamp.

There are different types of lamps used. Older torches often use incandescent lamps (light bulbs).

Activity 3.4: Let Us Observe

Inside an incandescent lamp's glass bulb, there is a very thin wire called the filament. When electric current flows through the filament, it gets very hot and glows, producing light.

The filament is supported by thicker wires connected to the lamp's terminals. These terminals are usually a metal tip at the base and the metal casing around the base. They are arranged so they do not touch each other, allowing the current to enter through one terminal, pass through the filament, and exit through the other terminal.

If the filament of an incandescent lamp is broken, it is called a fused lamp. A fused lamp cannot glow because the break in the filament prevents the electric current from flowing through it.

Many modern torches use Light Emitting Diodes (LEDs) instead of incandescent lamps. LEDs are more energy-efficient and durable.

Activity 3.5: Let Us Observe

Unlike incandescent lamps, LEDs do not have a filament inside.

LEDs also have two terminals, represented by wires. However, these terminals are not interchangeable like those of an incandescent lamp. An LED has a specific positive terminal (usually connected to a longer wire) and a specific negative terminal (the shorter wire). The way they are connected to the power source matters greatly.

Making An Electric Lamp Glow Using An Electric Cell Or Battery

Activity 3.6: Let Us Construct

To make a lamp glow using an electric cell or battery, we need to connect them properly using wires. Stripping the plastic covering from the ends of wires exposes the metal core needed for connections.

Components like cell holders and lamp holders can make connections easier, but wires can also be secured directly to terminals using electrical tape.

Experimenting with different connection arrangements between a cell and an incandescent lamp shows that the lamp glows only when there is a complete path for the electric current to flow from one terminal of the cell, through the lamp, and back to the other terminal of the cell.

An Electrical Circuit

The complete path through which electric current flows is called an electrical circuit.

For an incandescent lamp to glow, electric current must pass through its filament. This happens when the lamp's terminals are correctly connected to the cell's terminals, forming a closed circuit. If the circuit is broken anywhere (an open circuit), current cannot flow, and the lamp will not glow.

Conventionally, the direction of electric current in a circuit is considered to be from the positive terminal of the electric cell or battery to the negative terminal.

For incandescent lamps, the direction of current flow through the filament doesn't matter; they will glow as long as the circuit is complete.

Activity 3.7: Let Us Experiment

Making an LED glow requires careful attention to polarity.

Using two cells in a holder creates a battery with positive and negative terminals. When connecting an LED to this battery, the LED will glow only if its positive terminal (longer wire) is connected to the positive terminal of the battery and its negative terminal (shorter wire) is connected to the negative terminal of the battery.

If the LED's terminals are connected the other way around, it will not glow. This is because LEDs allow electric current to pass through them in only one direction.

Interesting Note: When cells are placed side-by-side in a battery compartment, metal strips or wires inside connect the positive terminal of one cell to the negative terminal of the next to form the series connection. Polarity symbols (+ and -) are often marked inside the compartment to guide correct placement.

Electric Switch

In devices like a torch, a switch is used to control the flow of electricity, turning the device on or off without disconnecting wires.

Activity 3.8: Let Us Construct

A simple switch can be made using drawing pins and a safety pin or paper clip on a piece of cardboard.

Activity 3.9: Let Us Test

Connecting this simple switch into a circuit with a cell and lamp shows its function:

• When the safety pin does not touch the second drawing pin, there is a gap in the circuit. This is the 'OFF' position or open circuit. Current cannot flow, and the lamp does not glow.
• When the safety pin touches the second drawing pin, it bridges the gap and completes the circuit. This is the 'ON' position or closed circuit. Current flows from the cell through the lamp, and the lamp glows.

A switch is a simple device that can either complete (close) or break (open) an electrical circuit, allowing us to control the flow of electricity as needed.

Circuit Diagrams

Drawing pictures of electrical circuits can be time-consuming and messy. To simplify representing circuits, standard symbols are used for each component.

In the symbol for an electric cell, the longer line represents the positive terminal, and the shorter, thicker line represents the negative terminal.

For an LED symbol, the triangle points in the allowed direction of conventional current flow (from positive to negative). The arrows indicate that light is emitted.

Using these symbols to draw a representation of an electrical circuit is called creating a circuit diagram. Circuit diagrams make it easy to understand how different components are connected and how the circuit is designed to function.

Activity 3.10: Let Us Draw

Using the standard symbols from the table below, we can draw clear diagrams for electrical circuits.

S.No.	Electrical Component	Symbol
1.	Electric cell
2.	Battery
3.	Electric lamp (Incandescent)
4.	Light Emitting Diode (LED)
5.	Switch in ‘ON’ position (Closed)
6.	Switch in ‘OFF’ position (Open)
7.	Wire

Important Note: Standard symbols are used globally by organizations like IEC, ANSI, and IEEE to ensure clarity and easy understanding of electrical circuits across different regions and industries.

Electrical Conductors And Insulators

When making electric circuits, we use connecting wires typically made of metal, often covered with plastic or rubber. Why are these specific materials used?

Activity 3.11: Let Us Identify

We can investigate which materials allow electricity to pass through them by creating a simple tester. This tester consists of an electric cell and a lamp connected by wires, leaving a gap between two free ends of the wires.

If the lamp glows when an object is placed in the gap, it means electric current flowed through the object, completing the circuit. If the lamp does not glow, current could not pass through the object.

Materials can be classified based on whether they allow electric current to flow:

• Conductors (Good Conductors): Materials through which electric current can pass easily. Metals are generally excellent conductors (e.g., silver, copper, gold). Copper is commonly used for wires due to its cost-effectiveness and availability.
• Insulators (Poor Conductors): Materials through which electric current cannot pass easily. Examples include plastic, rubber, glass, wood, paper, and ceramic.

S.No.	Object Tested	Material	Lamp Glows (Yes/No)	Conclusion (Conductor/Insulator)
1.	Metal Spoon	Metal	Yes	Conductor
2.	Plastic Scale	Plastic	No	Insulator
3.	Key	Metal	Yes	Conductor
4.	Rubber Eraser	Rubber	No	Insulator
5.	Glass Bangle	Glass	No	Insulator
6.	Aluminium Foil	Metal (Aluminium)	Yes	Conductor
7.	Wooden Block	Wood	No	Insulator
8.	Paper Strip	Paper	No	Insulator
9.	Pencil Lead	Graphite (Carbon)	Yes	Conductor
10.	Sewing Needle	Metal	Yes	Conductor

Understanding conductors and insulators is vital for safety. Conductors are used for the parts where electricity needs to flow (like wires, contact points in switches and plugs). Insulators are used to cover conductors (like the plastic coating on wires) and to make parts that people touch (like the casing of switches, plug tops) to prevent electric shocks. Our own bodies are conductors, making it dangerous to come into contact with live electrical parts.

Interesting Note: Electricity from batteries is typically Direct Current (DC), where the current flows in one direction. Electricity from power plants delivered to wall sockets is Alternating Current (AC), where the current direction changes periodically. DC is used for small, portable devices, while AC powers larger appliances and is used for widespread distribution.

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In a Nutshell:

• An electric cell provides portable electrical energy, having positive and negative terminals.
• A battery is a combination of two or more electric cells, usually connected positive terminal to negative terminal in series.
• An incandescent electric lamp uses a filament that heats up and glows when current passes through it.
• A Light Emitting Diode (LED) is a type of lamp that lights up when current flows through it in the correct direction (positive terminal connected to positive, negative to negative). LEDs do not have a filament.
• An electrical circuit is a complete path allowing electric current to flow from one terminal of the source, through the components, and back to the other terminal.
• A switch is a device used to open or close a circuit, controlling the flow of electricity. An open circuit (switch OFF) stops current; a closed circuit (switch ON) allows current.
• The conventional direction of electric current is from the positive to the negative terminal of the cell/battery.
• A circuit diagram uses standard symbols to represent the components and connections in an electrical circuit.
• Conductors are materials that easily allow electric current to pass through them (e.g., metals).
• Insulators are materials that do not allow electric current to pass through them easily (e.g., plastic, rubber, wood).
• Both conductors and insulators are essential in electrical devices, used strategically for function and safety.

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