Chemical effects of Electric Current
Lesson 14
Do Liquids conduct electricity?
✦ Activity 14.1
Join the free ends of the tester for a moment. This completes the circuit and the tester should
glow. However, if the bulb does not glow it means the tester is not working. Check if all connections
are tight. If they are then replace the bulb with another bulb. Now test and see if the bulb works.
✦ Activity 14.2
- Collect a few plastic or rubber bottle caps
- Pour 1 tsp of vinegar or lemon juice into this
- Bring the tester over the cap and let the free ends dip into them.
- Take care that they are not more than 1 cm apart or too close.
- When the liquid between the ends of the two testers allows the current to pass the circuit is
complete
- The current flows and the bulb glows.
- When the liquid does not let the current pass through the circuit is not complete and the bulb
doesn't glow.
✦ In some situations even though the liquid is conducting the bulb may not glow. Why?
- Due to the heating effect of the current, the filament of the bulb gets heated to a higher
temperature and it starts glowing.
- If the circuit is too weak the filament of the bulb does not get heated to a high temperature
and does not glow.
✦ Why is the current in the circuit weak?
- Though materials can conduct electricity it may not conduct it easily as metals.
- As a result the circuit of the bulb may be complete but still may not conduct electricity.
✦ LED
- Led glows when a weak current is present.
- One lead is slightly longer than the other.
- When connecting to a circuit the longer end is always connected to the positive terminal of
the battery and the shorter lead is connected to the negative terminal of the battery.
✦ Activity 14.3
- Take the tray from a discarded match box.
- Wrap an electric wire a few times around the tray.
- Place a small compass needle inside it.
- Now connect one end of the wire to the terminal of the battery.
Lesson 14
Do Liquids conduct electricity?
✦ Activity 14.1
Join the free ends of the tester for a moment. This completes the circuit and the tester should
glow. However, if the bulb does not glow it means the tester is not working. Check if all connections
are tight. If they are then replace the bulb with another bulb. Now test and see if the bulb works.
✦ Activity 14.2
- Collect a few plastic or rubber bottle caps
- Pour 1 tsp of vinegar or lemon juice into this
- Bring the tester over the cap and let the free ends dip into them.
- Take care that they are not more than 1 cm apart or too close.
- When the liquid between the ends of the two testers allows the current to pass the circuit is
complete
- The current flows and the bulb glows.
- When the liquid does not let the current pass through the circuit is not complete and the bulb
doesn't glow.
✦ In some situations even though the liquid is conducting the bulb may not glow. Why?
- Due to the heating effect of the current, the filament of the bulb gets heated to a higher
temperature and it starts glowing.
- If the circuit is too weak the filament of the bulb does not get heated to a high temperature
and does not glow.
✦ Why is the current in the circuit weak?
- Though materials can conduct electricity it may not conduct it easily as metals.
- As a result the circuit of the bulb may be complete but still may not conduct electricity.
✦ LED
- Led glows when a weak current is present.
- One lead is slightly longer than the other.
- When connecting to a circuit the longer end is always connected to the positive terminal of
the battery and the shorter lead is connected to the negative terminal of the battery.
✦ Activity 14.3
- Take the tray from a discarded match box.
- Wrap an electric wire a few times around the tray.
- Place a small compass needle inside it.
- Now connect one end of the wire to the terminal of the battery.
