Year 6 Science: Cells and their voltage
Part of the Year 6 Science cells, brightness and volume chapter. Chapter overview · whole chapter on one page
Cells and their voltage
A cell gives a voltage, measured in volts (V). A standard cell gives 1.5 volts. Cells have a positive end, marked +, and a negative end, marked -.
When cells are joined end to end, with positive to negative, their voltages add up. The total voltage is the number of cells multiplied by 1.5 volts.
The table gives the total voltage for one, two and three cells.
| Cells in the circuit | Total voltage (volts) |
|---|---|
| 1 | 1.5 |
| 2 | 3.0 |
| 3 | 4.5 |
Key ideas
- A standard cell gives 1.5 volts.
- Cells joined end to end, positive to negative, add their voltages.
- Total voltage = number of cells x 1.5 volts.
- More voltage means more push on the electricity in the circuit.
Method. Multiply the number of cells by 1.5 volts.
- Count the cells. There are two cells.2
- Multiply. Each cell gives 1.5 volts, so 2 x 1.5 volts.2 x 1.5 = 3.0
- Write the answer. 3.0 volts
Check. The table gives 3.0 volts for two cells. ✓
Method. Multiply the number of cells by 1.5 volts.
- Count the cells. There are three cells.3
- Multiply. So 3 x 1.5 volts.3 x 1.5 = 4.5
- Write the answer. 4.5 volts
Check. Adding 1.5 volts three times gives 4.5 volts. ✓
Method. Subtract the one-cell voltage from the three-cell voltage.
- Read the voltages. Three cells give 4.5 volts and one cell gives 1.5 volts.4.5 and 1.5
- Subtract. The difference is 4.5 minus 1.5.4.5 - 1.5 = 3.0
- Write the answer. 3.0 volts
Check. 1.5 + 3.0 = 4.5. ✓
Watch out
Watch out: cells must be joined positive to negative to add their voltages. A cell joined the wrong way round takes away voltage from the others.
Exam tip
Exam tip. Multiply the number of cells by 1.5 volts, and give the unit: volts.
Try it (with your teacher, or a grown-up at home). With a teacher, look at the labels on two cells. Find the + and - ends. Join them end to end, + to -, and read the label or the chart that says the voltage. Never join the two ends of one cell with a wire, because that is a short circuit and makes the cell hot.
Exercise 9A Cells and their voltage
Method. Read the fact.
- Read the fact. A standard cell gives 1.5 volts.1.5
- Write the answer. 1.5 volts
Check. The table gives 1.5 volts for one cell. ✓
Method. Read the description.
- Read the description. A cell has a positive end, marked +, and a negative end, marked -.positive
- Write the answer. positive
Check. The negative end is marked -. ✓
Method. Read the table.
- Read the table. The table gives 3.0 volts for two cells.3.0
- Write the answer. So the total voltage is 3.0 volts.3.0 volts
- Write the answer. 3.0 volts
Check. 2 x 1.5 = 3.0. ✓
Method. Read the table.
- Read the table. The table gives 4.5 volts for three cells.4.5
- Write the answer. So the total voltage is 4.5 volts.4.5 volts
- Write the answer. 4.5 volts
Check. 3 x 1.5 = 4.5. ✓
Method. Read the rule.
- Read the rule. Cells joined end to end, positive to negative, add their voltages.add up
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. Each cell adds 1.5 volts. ✓
Method. Read the fact.
- Read the fact. Voltage is measured in volts, abbreviated V.volts
- Write the answer. V
Check. Volts are written as V. ✓
Method. Read the fact.
- Read the fact. One cell gives 1.5 volts.1.5
- Write the answer. 1.5 volts
Check. A standard cell is 1.5 volts. ✓
Method. Multiply by 1.5 volts.
- Multiply. Four cells give 4 x 1.5 volts.4 x 1.5 = 6.0
- Decide. So the answer is yes.yes
- Write the answer. yes
Check. Four cells give 6.0 volts. ✓
Method. Multiply the cells by 1.5 volts.
- Multiply. Three cells give 3 x 1.5 volts.3 x 1.5 = 4.5
- Write the answer. 4.5 volts
Check. 1.5 + 1.5 + 1.5 = 4.5. ✓
Method. Multiply the cells by 1.5 volts.
- Multiply. Five cells give 5 x 1.5 volts.5 x 1.5 = 7.5
- Write the answer. 7.5 volts
Check. Half of 15 is 7.5. ✓
Method. Check the table.
- Check the table. Three cells give 4.5 volts, not 3.0 volts.4.5
- Decide. So Mo is not right.no
- Write the answer. no
Check. 3.0 volts is the voltage of two cells. ✓
Method. Think about the direction.
- Think about the joining. Positive to negative lets each voltage add to the next.add
- Think about the wrong way. A cell joined the wrong way takes voltage away.takes away
- Write the answer. Accept any sentence that says joining positive to negative makes the voltages add up, while a cell the wrong way takes voltage away.
Check. The direction of the cells matters. ✓
Method. Think about adding.
- Think about each cell. Each cell gives 1.5 volts.1.5
- Think about the total. Joined end to end, the voltages add: 1.5 + 1.5 = 3.0 volts.3.0
- Write the answer. Accept any sentence that says the voltages of the two cells add together, so the total voltage is 1.5 + 1.5 volts.
Check. Two cells, each 1.5 volts, add to 3.0 volts. ✓