Year 6 Science: Reading and drawing a circuit diagram
Part of the Year 6 Science components, switches and circuit symbols chapter. Chapter overview · whole chapter on one page
Reading and drawing a circuit diagram
To read a circuit diagram, follow the lines round the loop. Check three things:
- Is every component joined in one complete loop?
- Is there a cell to give the voltage?
- Is the switch closed, so that there is no gap?
If all three are true, current flows, and the bulb lights.
Key ideas
- Follow the lines round the loop to check the circuit.
- A complete loop with a cell and a closed switch lights the bulb.
- An open switch makes a gap, so the bulb does not light.
- Draw each part with its symbol, and join them with straight lines.
Method. Look at the switch symbol.
- Read the symbol. The switch symbol is a line with no gap, joined all the way across.no gap
- Write the word. So the switch is closed.closed
- Write the answer. closed
Check. A closed switch completes the loop. ✓
Method. Check the switch.
- Check the switch. The switch is open, so there is a gap in the loop.gap
- Decide. With a gap, no current flows, so the answer is no.no
- Write the answer. no
Check. Open means the bulb is off. ✓
Method. Count the parts in the loop.
- Count. The loop has a cell, a closed switch and a bulb.three parts
- Write the number. So there are 3 symbols.3
- Write the answer. 3
Check. The wires are not counted as components. ✓
Watch out
Watch out: a circuit diagram shows the path of the current, not the position of the parts on the page. Follow the lines, not the shapes.
Exam tip
Exam tip. When you read a circuit, check the loop is complete, the cell is there, and the switch is closed before you say a bulb lights.
Try it (with your teacher, or a grown-up at home). Draw a circuit with a cell, a closed switch and a bulb, using the symbols in this chapter. Then draw the same circuit with the switch open. Ask a partner to say whether the bulb lights in each diagram.
Exercise 10E Reading and drawing a circuit diagram
Method. Look at the switch symbol.
- Read the symbol. The symbol has no gap.no gap
- Write the word. So the switch is closed.closed
- Write the answer. closed
Check. A closed switch completes the loop. ✓
Method. Look at the switch symbol.
- Read the symbol. The symbol has a gap in it.gap
- Write the word. So the switch is open.open
- Write the answer. open
Check. An open switch is a gap. ✓
Method. Check the three things.
- Check the loop. The loop is complete, there is a cell, and the switch is closed.all three
- Decide. So current flows and the bulb lights.yes
- Write the answer. yes
Check. All three checks are true. ✓
Method. Check the switch.
- Check the switch. The switch is open, so there is a gap.gap
- Decide. So no current flows, and the bulb does not light.no
- Write the answer. no
Check. Open means off. ✓
Method. Count the parts.
- Count. The loop has a cell, an open switch and a bulb.three
- Write the number. So there are 3 symbols.3
- Write the answer. 3
Check. The cell, switch and bulb are the three parts. ✓
Method. Read the loop.
- Read the loop. The cell is the part that gives the voltage.voltage
- Write the word. So the part is the cell.cell
- Write the answer. cell
Check. Without a cell there is no voltage. ✓
Method. Read the idea.
- Read the idea. A complete loop has no gaps.no gaps
- Decide. So a loop with a gap is not complete, and the answer is no.no
- Write the answer. no
Check. Current cannot flow through a gap. ✓
Method. Recall the standard cell.
- Recall. A standard cell gives 1.5 volts.1.5
- Write the answer. 1.5
Check. The bulb lights because of this voltage. ✓
Method. Multiply by 1.5 volts.
- Multiply. Two cells give 2 x 1.5 volts.2 x 1.5 = 3.0
- Write the answer. 3.0 volts
Check. Two cells add their voltages. ✓
Method. Check the open switch.
- Check the switch. The open switch is a gap, so no current flows, even with a cell.gap
- Decide. So Ruby is not right.no
- Write the answer. no
Check. The cell alone does not light a bulb in an open loop. ✓
Method. Think about the gap.
- Think about the gap. The open switch makes a gap in the loop.gap
- Think about the current. So the current cannot flow round to the bulb.cannot flow
- Write the answer. Accept any sentence that says the open switch is a gap in the loop, so the current cannot flow round to the bulb.
Check. A complete loop is needed for the bulb to light. ✓
Method. Think about the diagram.
- Think about the picture. Without symbols, each part must be drawn or described in full.drawn in full
- Think about the reader. That makes the diagram slow to read and hard to follow.hard to follow
- Write the answer. Accept any sentence that says without symbols, each component would need a long description, so the diagram would be hard to follow.
Check. Symbols make diagrams quick to read. ✓