What makes a lamp light?
Objective: Explain whether a lamp lights in a simple battery circuit by checking the complete path and the energy source.
Safety first
Use only this on-screen model or a paper drawing. Do not put objects into sockets, open an electrical device, or try this with household electricity. This lesson does not ask you to assemble any real circuit.
Before you start
- Recognize a battery, wire, switch and lamp.
- Use on, off, open and closed to describe a switch.
An open switch leaves a gap. A closed switch connects the path. Here “closed” means connected, not switched off.
What this model assumes: one charged battery matched to one working filament lamp, conducting wires, one switch and a single series path; the lamp has two separate contacts, one connected to each side of the battery through the loop; no short circuit, parallel branch, capacitor, LED polarity, mains electricity or numeric brightness prediction; a settled on/off state without switching transients, warm-up delay, wire heating, internal resistance or battery depletion.
Explanation
A battery, wires, a lamp and a switch can form one continuous loop. The loop goes from one battery terminal, through the lamp, and back to the other terminal. In this lesson, the battery is charged, the lamp works, and the wires conduct.
A closed switch completes the path. Electric charge can flow around the circuit, and the lamp lights. An open switch makes a gap. In this simple circuit, there is then no sustained current around the loop, and the lamp is off. A wire reaching only one lamp contact is not a complete path.
The battery also supplies energy. Its chemical energy decreases as energy is transferred electrically to the lamp and the rest of the circuit. The filament lamp gives out light and warms its surroundings. The energy has changed form and spread out; it has not disappeared.
Current is the flow of electric charge. The lamp does not use up the charge as if it were fuel. The battery supplies energy to the circuit while charge continues around a complete loop.
Use two questions when you explain the model: Is there a complete conducting path through the lamp and battery? Is a suitable working energy source present? A drawn loop alone is not enough if its battery has no usable stored energy.
Worked example
The charged battery and lamp are connected, but the switch is open.
- The open switch makes a gap in the only path.
- There is no sustained current around the loop in this model.
- The lamp stays off. Closing the switch completes the path and lets the battery supply energy to the lamp.
In words: battery terminal A connects by wire to an open switch. The other side of the switch connects to lamp contact A. Lamp contact B connects by wire to battery terminal B. There is a gap at the switch.
Open and close the path
Close the switch, then open it again. Read what happens to the lamp and the path.
State: Switch open. There is a gap in the path. Lamp off. No sustained current flows around this simple loop.
Battery terminal A connects by wire to the switch. The other side of the switch connects to lamp contact A. Lamp contact B connects by wire to battery terminal B. There is a gap at the switch.
Hint 1
Trace the path from one battery terminal, through the lamp, and back to the other.
Hint 2
An open switch leaves a gap; a closed switch joins its two contacts.
Answer with explanation
Answer: option A. Closing the switch completes the conducting path. It does not create energy; the battery’s chemical energy supplies the circuit.
Practice: three questions
A common mix-up
Claim to check: “The bulb uses up the current.”
The lamp transfers energy to light and thermal energy. Electric charge continues around the complete single loop; it is not used up by the lamp.
Try it on paper (optional, not graded)
Sketch a battery-powered torch with one lamp. Mark one place where an imaginary gap would stop it lighting. Explain what supplies the energy when it is on, and name two ways that energy leaves the lamp.
No drawing? Describe the loop aloud or in writing instead. Name the two battery terminals, the lamp’s two contacts and a possible gap.
Use paper or words only. Do not open or modify a torch or any other device.
Model answer
A gap at the switch or any wire in the only loop stops sustained current. The battery’s chemical energy supplies the circuit, and the lamp gives out light and warms its surroundings.
This free sample works on its own. Review the explanation or try the activity again.