Year 4 Science: More cells and the brightness of a lamp
Part of the Year 4 Science electricity and circuits chapter. Chapter overview · whole chapter on one page
More cells and the brightness of a lamp
In a series circuit, a second cell adds more push to the electricity. With two cells, more electricity flows through the lamp, so the lamp is brighter. The fair test changes only the number of cells.
The table shows the results of the fair test, with one cell and with two cells.
| Number of cells in the circuit | Brightness of the lamp |
|---|---|
| 1 | dim |
| 2 | brighter |
Key ideas
- A series circuit with two cells gives a brighter lamp than one cell.
- In a fair test, change only the number of cells.
- Keep the bulb, the wires and the holder the same.
- This is practice: the statements are about the loop, not the number of cells.
Method. Read the table.
- Read the row. The row for one cell says the lamp is dim.dim
- Check the other row. The row for two cells says brighter, so the one-cell lamp is the dimmer one.dimmer
- Write the answer. dim
Check. One cell gives the dimmer lamp. ✓
Method. Subtract the first number of cells from the second.
- Read the numbers. The first test has 1 cell, and the second has 2 cells.2 and 1
- Subtract. 2 minus 1 is 1.1
- Write the answer. 1
Check. Check: 1 plus 1 makes 2. ✓
Method. Compare the two brightness words.
- Read the table. The row with two cells says brighter.brighter
- Choose the number. So two cells give the brighter lamp.2
- Write the answer. 2
Check. Two cells gives more electricity through the lamp. ✓
Watch out
Watch out: a second cell does not make a bulb brighter if the loop is broken. The loop must be complete first.
Try it at home or school (with a grown-up). With a grown-up, make a complete loop with one cell and a bulb holder. Then add a second cell in the same line, and watch the bulb. Keep the wires and the bulb the same. Do not touch the bulb while it is hot.
Exam tip
Grown-up tip. Ask: “What did you change? What did you keep the same?” Let your child change only the number of cells, and compare the brightness.
Exercise 9E More cells and the brightness of a lamp
Method. Read the one-cell row.
- Read the row. The one-cell row says dim.dim
- Write the answer. dim
Check. One cell is the dimmer test. ✓
Method. Read the two-cell row.
- Read the row. The two-cell row says brighter.brighter
- Write the answer. brighter
Check. Two cells is the brighter test. ✓
Method. Subtract the cells.
- Read the numbers. The tests have 2 and 1 cells.2 and 1
- Subtract. 2 minus 1 is 1.1
- Write the answer. 1
Check. Check: 1 plus 1 makes 2. ✓
Method. Read the brightness column.
- Read the brighter row. The brighter lamp has two cells.two cells
- Write the answer. 2
Check. Two cells is brighter than one. ✓
Method. Read the dim row.
- Read the row. The dim row has 1 cell.1
- Write the answer. 1
Check. One cell gives a dim lamp. ✓
Method. Read the table in section 9.5.
- Read the table. The two-cell row says brighter.brighter
- Decide. So a second cell makes the lamp brighter, and the answer is yes.yes
- Write the answer. yes
Check. More cells give more push to the electricity. ✓
Method. Read the safe practice in section 9.5.
- Read the practice. Practicals use cells and a bulb holder.bulb holder
- Write the answer. bulb holder
Check. A bulb holder keeps the bulb in place. ✓
Method. Count the cells in the circuit.
- Count the cells. The circuit has one cell.one cell
- Write the answer. 1
Check. One cell is the first test. ✓
Method. Read the table in section 9.5.
- Read the table. The two-cell row says the lamp is brighter, not broken.brighter
- Decide. So Sam is not right.no
- Write the answer. no
Check. Two cells gave a brighter lamp in the test. ✓
Method. Read the table in section 9.5.
- Read the table. The table says two cells give a brighter lamp.brighter
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. Two cells is brighter than one. ✓
Method. Think about a fair test.
- Think about the test. Only the number of cells changes, so the bulb, the wires and the holder must stay the same.stay the same
- Write one thing. For example, use the same bulb each time.same bulb
- Write the answer. Accept any one thing, such as: the same bulb, the same wires, or the same holder.
Check. Change one thing only to keep the test fair. ✓
Method. Think about the cell.
- Think about the push. One cell gives a smaller push to the electricity.smaller push
- Write the reason. So less electricity flows through the lamp, and it is dim.dim
- Write the answer. Accept any sentence that says one cell gives less push to the electricity, so less electricity flows and the lamp is dim.
Check. More cells give more push, so the lamp is brighter. ✓