Open the loop, close the loop
A switch breaks a circuit or completes it.
Where does it go?
A switch is a simple device in a circuit. It is in the top wire of a loop with a cell and a lamp.
If we move the switch to the bottom wire, will it still switch the lamp ON and OFF?
What this lesson covers
The idea
A switch completes or breaks a circuit: when ON the circuit is closed and current flows; when OFF the circuit is open and no current flows. A switch can be placed anywhere in a circuit.
Where does it go?
A switch is a simple device in a circuit. It is in the top wire of a loop with a cell and a lamp.
If we move the switch to the bottom wire, will it still switch the lamp ON and OFF?
- Yes, it works from any place in the loop
- No, only from the top wire
- Only next to the cell
Move the switch
Turn the switch ON and OFF. Then move it to other gaps in the loop and try again.
Open and closed
A switch completes or breaks a circuit. When it is ON the circuit is closed and current flows. When it is OFF the circuit is open and no current flows. A switch can be placed anywhere in a circuit.
The switches for lights at home work the same way, though they are designed differently.
- Switch | Circuit | Current | Lamp
- ON | closed | flows | glows
- OFF | open (there is a gap) | does not flow | dark
Notes
ON: circuit closed, current flows. OFF: circuit open, no current. A switch can be placed anywhere in a circuit.
Check yourself
When a switch is OFF, the circuit is...
A lamp glows in a circuit with a switch. What is the switch doing?
Where in a circuit can a switch be placed?
Why does the lamp go dark when the switch is turned OFF?
- closed. A closed circuit has current flowing. OFF means the path has a gap.
- open — correct. Yes! The gap stops the current.
- broken forever. It is not broken. Turning the switch ON closes it again.
- It is OFF, so the circuit is open. An open circuit would make the lamp dark.
- It is ON, so the circuit is closed — correct. Yes! The closed circuit lets the current flow.
- It does not matter. It matters: the switch decides whether the path is complete.
- Only next to the cell. A switch works from any place in the loop.
- Only next to the lamp. A switch works from any place in the loop.
- Anywhere in the circuit — correct. Yes! Any gap in the loop will do.
- The gap in the switch breaks the path, so current cannot flow — correct. Yes! No complete path, no current.
- The cell is used up. The cell is fine. It is the path that is broken.
- The lamp forgets how to glow. The lamp is fine. It needs a complete path.