Year 6 Science: Switches: open and closed
Part of the Year 6 Science components, switches and circuit symbols chapter. Chapter overview · whole chapter on one page
Switches: open and closed
A switch is a component that can open or close a circuit.
- When a switch is open, there is a gap in the loop. No current flows, so the bulb and buzzer are off.
- When a switch is closed, the loop is complete. Current flows, so the bulb and buzzer are on.
Six tests were made with one switch in a loop with a bulb. The table shows each test.
| Test | Switch | Bulb lit? |
|---|---|---|
| Test 1 | open | no |
| Test 2 | closed | yes |
| Test 3 | closed | yes |
| Test 4 | open | no |
| Test 5 | closed | yes |
| Test 6 | open | no |
Key ideas
- A switch that is open makes a gap in the loop, so no current flows.
- A switch that is closed makes the loop complete, so current flows.
- The bulb is lit only when the switch is closed and the loop is complete.
- A switch is a safe way to turn a circuit on or off.
Method. Count the rows that say closed.
- Read the table. The rows that say closed are tests 2, 3 and 5.closed
- Count. That is three tests.3
- Write the answer. 3
Check. Three tests were closed and three were open. ✓
Method. Read test 4.
- Read the row. Test 4 has the switch open.open
- Decide. With the switch open there is a gap, so the bulb is not lit: the answer is no.no
- Write the answer. no
Check. The table says no for test 4. ✓
Method. Count the rows that say yes.
- Read the last column. The bulb lit in tests 2, 3 and 5.yes
- Count. So the bulb lit in 3 tests.3
- Write the answer. 3
Check. The bulb lit only when the switch was closed. ✓
Watch out
Watch out: a closed switch does not mean the circuit is broken. A closed switch completes the loop; an open switch breaks it.
Exam tip
Exam tip. Say that an open switch makes a gap, so no current flows, and a closed switch completes the loop.
Try it (with your teacher, or a grown-up at home). With a teacher, build a loop with one cell, one bulb and a switch. Open and close the switch, and watch the bulb. Write down the position of the switch and whether the bulb is on, each time you test it.
Exercise 10B Switches: open and closed
Method. Read the definition.
- Read the definition. An open switch has a gap in the loop.gap
- Write the word. So the switch is open.open
- Write the answer. open
Check. No current flows through an open switch. ✓
Method. Read the definition.
- Read the definition. A closed switch completes the loop, so current flows.completes
- Write the word. So the switch is closed.closed
- Write the answer. closed
Check. A closed switch lets current flow. ✓
Method. Think about the gap.
- Think about the gap. An open switch makes a gap, which stops the current.stops
- Decide. So no current flows, and the answer is no.no
- Write the answer. no
Check. The gap breaks the loop. ✓
Method. Think about the loop.
- Think about the loop. A closed switch completes the loop, so current flows through the bulb.flows
- Write the word. So the bulb is on.on
- Write the answer. on
Check. The bulb lights when current flows. ✓
Method. Count the rows that say open.
- Read the table. The open tests are 1, 4 and 6.open
- Count. That is three tests.3
- Write the answer. 3
Check. Three open and three closed makes six tests. ✓
Method. Read test 6.
- Read the row. Test 6 has the switch open.open
- Decide. So the bulb was not lit, and the answer is no.no
- Write the answer. no
Check. Test 6 shows no. ✓
Method. Count the yes rows.
- Read the table. The bulb was lit in tests 2, 3 and 5.yes
- Count. That is three tests.3
- Write the answer. 3
Check. The yes rows match the closed switches. ✓
Method. Read the idea.
- Read the idea. A switch opens the loop, so the circuit can be turned off without removing wires.without removing wires
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. Opening a switch is quicker than unplugging wires. ✓
Method. Check the open switch.
- Check the rule. An open switch makes a gap, so no current flows and the bulb is off.off
- Decide. So Priya is not right.no
- Write the answer. no
Check. Open means off, and closed means on. ✓
Method. Check the loop.
- Check the loop. The loop is complete, because the switch is closed.complete
- Decide. So current flows and the bulb lights, and the answer is yes.yes
- Write the answer. yes
Check. This matches test 2 in the table. ✓
Method. Count all the tests.
- Count the tests. There were six tests in total.6
- Decide. All six tests were needed to show the pattern, so the answer is 6.6
- Write the answer. 6
Check. Three open and three closed tests showed the pattern. ✓
Method. Think about the gap.
- Think about the cell. The cell is still connected, but the loop has a gap.gap
- Think about the current. So the current cannot flow round, and the bulb goes off.cannot flow
- Write the answer. Accept any sentence that says the open switch makes a gap in the loop, so current stops flowing even though the cell is connected.
Check. The gap is the reason, not the cell. ✓
Method. Think about one loop.
- Think about the path. The current flows along one loop, through every component in turn.one loop
- Think about the gap. A gap anywhere in that path stops the current everywhere.everywhere
- Write the answer. Accept any sentence that says the loop is one path, so a gap at any point stops the current everywhere in the loop.
Check. One loop means one path for the current. ✓