BananaLearnLearning LibraryGamesGrade 5 · Science
Touching one wire to a bulb is not enough to light it. A working circuit needs a continuous conducting path through the bulb and back to the cell.
A simple working circuit joins both terminals of a suitable cell to the two contacts of a compatible bulb through conducting wires. Opening a switch breaks the path and stops the current.
Before you start: Identify a cell, wires and a small bulb. Use only a suitable low-voltage school circuit kit with adult supervision.
A simple circuit needs a continuous path from one cell terminal, through the component, and back to the other terminal. In a filament bulb, the path enters through one metal contact, passes through the filament and leaves through the other contact. Touching both wires to the same contact does not make current pass through the filament.
A cell has two terminals. In a circuit symbol the longer line is positive and the shorter line is negative. The symbol describes connections rather than the physical shape of the holder. A wire that looks close to a contact in a drawing must actually be connected in the real model.
A closed switch joins its contacts so the conducting path is complete. An open switch separates them. The cell can still be present and the wires can still surround the bulb, but the gap prevents the ordinary circuit current.
Do not teach that electricity is used up before returning to the cell. Energy is transferred from the cell to the bulb and surroundings; the circuit provides a path for charge. At this level, tracing the complete path and distinguishing energy transfer from a missing connection are enough.
| Observation | Possible explanation | Check safely |
|---|---|---|
| No light | Open switch or loose contact | Trace each connection with power disconnected. |
| No light with a complete route | Flat cell or broken bulb | Ask an adult to substitute a known working part. |
| Light with switch closed | Working complete circuit | Open the switch and compare. |
| Wire or cell becomes warm | Unsafe connection or fault | Disconnect immediately and tell an adult. |
An adult can place a test object in a gap in a low-voltage kit circuit. Keep the cell, bulb and wires the same. A metal paper clip may complete the path; a dry plastic ruler usually will not. Contact must be good before interpreting a result.
A bulb that stays dark does not by itself prove the material is an insulator: a loose clip or flat cell can produce the same observation. Test the working circuit before and after inserting the object. Record both the material and the observation.
Use only a purpose-made, low-voltage kit and its instructions. Never use a wall socket, mains appliance, exposed household wire or liquid as a classroom test. Never connect the two cell terminals directly with a wire: a short circuit can heat the wire and cell.
Keep small cells and components away from young children. Stop if a part becomes hot, damaged or leaks. This page explains the concept; it does not replace the kit’s adult-supervision and battery safety instructions.
Attempt a short group of questions before opening the solutions. Use a drawing or written method where helpful. Explain the answer, then try a similar question with a detail changed.
No; it completes that part of the path
Closed means the contacts join.
Metal conducts; the covering insulates
The materials perform different jobs.
The bulb may go off or flicker
The path is interrupted intermittently.
Supply electrical energy
Current is a flow of charge in the circuit.
No
A short circuit can cause overheating.
Yes
An ordinary simple circuit needs a complete loop.
Breaks the conducting path
A visible surrounding loop can still contain an electrical gap.
The path does not pass through the filament
Use the two different bulb contacts in the intended holder.
Not by itself
Rule out loose contacts and a flat cell.
Cell, bulb, wires and connections except the test object
Changing several things makes the result hard to interpret.
Disconnect and tell an adult
Do not continue testing a possible short circuit.
No
Mains electricity is dangerous.
Yes
Energy from the cell is transferred as light and heat.
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