Electricity: Circuits and their Components · Lesson 1 of 6
Electric Cells, Batteries, and the Torch
“Discover how a torch uses a portable energy source and why the order of its cells matters.”
• Group familiar uses of electricity and identify common sources of electrical energy. • Identify the lamp, switch, and cells in a torch. • Recognise the positive and negative terminals of a cylindrical cell. • Explain how correctly connected cells form a battery. • Choose safe ways to observe portable cells and their uses.
Electricity Around Us
Think of the first hour of your day. A light may help you get dressed, a fan may move air, and a phone may bring a message. Electricity supports many different tasks, so a list of electrical devices quickly becomes very long. Grouping those tasks helps us notice what electricity allows each device to do.
A class visiting the Bhakra Nangal Dam would see an important connection: falling water can be used to generate electricity. Wind, sunlight, flowing or falling water, and fuels such as coal and natural gas can be used in different generating systems. Electricity from a power station reaches buildings through a network of wires. A torch, however, carries its own small source, so it does not have to remain connected to a wall socket.
| Use | Familiar examples | Another way to think about the group |
|---|---|---|
| Lighting | Room lights, street lights, a torch | Producing light |
| Cooking | Electric kettle, toaster, mixer grinder | Heating food or moving blades |
| Heating and cooling | Heater, refrigerator, fan, air conditioner | Heating, cooling, or moving air |
| Transportation | Electric train, lift, electric scooter | Producing movement |
| Entertainment | Television, radio | Producing images and sound |
| Communication | Mobile phone, internet equipment | Sending and receiving information |
| Other work | Water pump, crane, computer | Moving water or loads, processing information |
These groups are useful, but they are not completely separate. A phone can support both communication and entertainment. A fan changes how comfortable we feel by moving air. We could instead group devices by the place where they are used, or by whether they mainly produce light, heat, sound, or movement. A good grouping states its rule rather than treating every device as belonging to only one possible category.
Problem
Should a lift be placed under transportation or under devices that produce movement?
- 1.A lift carries people between floors, so transportation describes its use.
- 2.Its motor produces movement, so the second category also fits.
- 3.Both are reasonable because the two grouping systems ask different questions. State which grouping rule you are using.
Use only the small cells, holders, and components approved by your teacher for these investigations. Never connect an experiment to a wall socket, household wiring, a portable generator, or a vehicle battery. Do not open a sealed cell, damage it, or connect its two terminals directly with a wire.
What Is Inside a Torch?
A torch is a useful starting point because its main parts can be identified without studying a large electrical appliance. Its lamp produces light, its cells supply electrical energy, and its switch controls when the lamp can operate. First observe the whole device, and then connect your observations to these parts.
With a teacher, use a torch whose cell compartment is meant to be opened. Move its switch to one position and observe the lamp. Move the switch back and observe again. You should find that one position makes the lamp glow and the other stops it glowing. Record what you see before proposing a reason: the switch changes something inside the electrical arrangement, rather than becoming a new source of energy.
Open only the ordinary cell compartment and identify the cells. Some torches contain two or more removable cells; others have a sealed rechargeable source that should be left closed. The observation gives us a question for later lessons: how do the cells, lamp, and switch work together to produce light?
Problem
A working torch stops shining when its switch is moved. Does that show that its cells have suddenly become empty?
- 1.The observation is linked to moving the switch.
- 2.Move it back to the working position. If the lamp shines again, the cells still supply energy.
- 3.The switch controls the electrical connection. The brief OFF period does not show that the source has been used up.
A Cell Has Two Terminals
To use a cell, we need places where connections can be made. Those connection points are called terminals. Look at an ordinary cylindrical torch cell from both ends: the small raised metal cap and the flat metal disc are different parts, and the printed signs tell us which is which.
A portable source of electrical energy with a positive terminal and a negative terminal.
For the cylindrical cell shown, the raised cap is the positive terminal, identified by +. The flat metal disc is the negative terminal, identified by −. Turn the cell over and read both signs. The wrapper is not an extra terminal. Different shapes of cells may look different, so use the labels and the device instructions instead of assuming that every cell has the same shape.
Problem
On a cylindrical torch cell, one end has a raised metal cap and a + sign. What is the other terminal?
- 1.The labelled cap identifies the positive terminal.
- 2.The opposite flat metal disc is the negative terminal, normally labelled −.
- 3.Connections must be made to the intended metal terminals; touching an arbitrary part of the wrapper does not serve the same purpose.
Connecting Cells to Make a Battery
Many devices are designed to use more than one cell. The arrangement matters: placing cells near each other is not enough. In the battery arrangement used here, the positive terminal of one cell connects to the negative terminal of the next. The two remaining end terminals connect the battery to the rest of the device.
In this chapter, two or more cells connected together so that they can supply electrical energy as one source. Everyday language also uses “battery” for some single-cell sources.
With your teacher, inspect a torch designed for two cells. Record the correct positions before changing them. Compare the working arrangement with one in which a cell has been reversed, and then restore the correct positions. With two similar cells in this simple torch, reversing one cell can make their effects oppose each other and the lamp does not work as intended. Adding more cells or trying random arrangements is not a suitable way to repair the torch.
A battery compartment may place cells beside one another rather than in a straight line. A metal strip can connect the positive end of one to the negative end of the other. Follow that connection and read the printed + and − signs. The way the cells are arranged physically can change while the connection rule stays the same.
Using the specified number of cells provides the source the device was designed to use. More connected cells can provide more stored energy, but the running time also depends on the device and how it uses that energy. Do not assume that doubling the number always doubles the running time, and do not add extra cells beyond the device instructions.
Problem
Four cylindrical cells are joined end-to-end, each positive end touching the next negative end. Which ends are available to the device?
- 1.There are three connections between neighbouring cells. Each joins unlike terminals.
- 2.The negative end of the first cell and the positive end of the fourth cell remain free.
- 3.Those two free ends are the battery terminals. The connected middle terminals are not four separate sources for the lamp.
Portable Sources for Different Jobs
The source must fit the device and its task. A wall clock, hearing aid, and electric vehicle all use portable electrical sources in different ways. Shape, size, and whether a source can be recharged are practical features; they do not remove the need for correct terminal connections.
| Source type | Typical uses | What to notice |
|---|---|---|
| Cylindrical cells | Torches, clocks, remotes, some toys | Read the end signs and compartment directions. |
| Button cells | Watches and some hearing aids | Small round shape; keep them away from young children. |
| Rechargeable batteries | Phones, laptops, electric vehicles | Use the approved charger and follow the device instructions. |
For a small investigation, ask an adult or a shopkeeper to help identify cell types used in familiar devices. Make a report with the source shape, whether it is rechargeable, and the device in which it is used. Observing labels and asking questions is enough; do not dismantle, test, or charge unfamiliar sources.
Quiz
Which part supplies electrical energy in an ordinary cell-powered torch?
Which description identifies the positive terminal of the cylindrical cell discussed here?
How should neighbouring cells be connected in the battery arrangement taught here?
Cells are side-by-side in a compartment. What is the best way to check their connection?
A phone appears in both communication and entertainment groups. What does this show?
Which source is suitable for a teacher-approved simple circuit investigation?
Practice Problems
- Group a torch, an electric kettle, a radio, and a lift by their main use.
- Describe two observations that help identify the terminals of a cylindrical torch cell.
- Draw three cells in a line and show the connections needed to make the battery arrangement studied here.
- Explain how cells beside one another can form the same kind of battery as cells in a line.
- A torch works before a student reverses one of its two similar cells. Explain what should be checked first.
- Plan a safe report comparing a clock cell, a watch cell, and a phone battery.
Torch: lighting; kettle: cooking/heating; radio: entertainment; lift: transportation. Explain any alternative grouping rule.
Key Takeaways
• Electricity supports light, heating, cooling, movement, sound, communication, and other work. • A torch combines an energy source, a lamp, and a switch. • A cell has positive and negative terminals; identify them from the correct signs and parts. • The battery arrangement studied here joins unlike terminals of neighbouring cells. • Follow compartment contacts and use only the specified source for each device. • Investigate with approved small cells and components under supervision.
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Electric Lamps and LEDs