Year 6 Science: Volume of a buzzer and the number of cells
Part of the Year 6 Science cells, brightness and volume chapter. Chapter overview · whole chapter on one page
Volume of a buzzer and the number of cells
A buzzer makes a sound when a current flows through it. A higher voltage makes more current flow, so the buzzer can be louder. The loudness in this table is a rating given by the class, out of 5.
As with the bulb, more cells give a higher total voltage. Each extra cell adds 1.5 volts.
The table gives the total voltage and the ratings for each number of cells.
| Number of cells | Total voltage (V) | Bulb brightness (out of 5) | Buzzer loudness (out of 5) |
|---|---|---|---|
| 1 | 1.5 | 2 | 2 |
| 2 | 3.0 | 4 | 3 |
| 3 | 4.5 | 5 | 5 |
Key ideas
- More cells give a higher voltage, and a louder buzzer.
- Loudness is recorded as a rating out of 5, using the same scale each time.
- A buzzer needs a complete circuit to make a sound.
- Compare the ratings with the table, not with memory.
Method. Read the row for two cells.
- Read the row. The row for two cells gives a loudness of 3 out of 5.3
- Write the answer. So the rating is 3 out of 5.3 out of 5
- Write the answer. 3 out of 5
Check. The rating goes up as the cells increase. ✓
Method. Subtract the one-cell rating from the three-cell rating.
- Read the ratings. The ratings are 5 for three cells and 2 for one cell.5 and 2
- Subtract. The difference is 5 minus 2.5 - 2 = 3
- Write the answer. 3 points
Check. 2 + 3 = 5. ✓
Method. Read the voltage column.
- Read the table. Three cells give 4.5 volts.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. ✓
Watch out
Watch out: the buzzer rating is a class rating out of 5. It is not a measurement in decibels, so do not give it a unit.
Exam tip
Exam tip. Link the volume to the cells: more cells, a higher voltage, and a louder buzzer.
Try it (with your teacher, or a grown-up at home). With a teacher, connect a buzzer to one cell, then to two cells joined end to end. Ask the class to rate each buzzer out of 5, using the same scale each time. Write the ratings in a table. Do not hold the buzzer near your ears.
Exercise 9C Volume of a buzzer and the number of cells
Method. Read the table.
- Read the table. The one-cell buzzer is rated 2 out of 5.2
- Write the answer. 2
Check. One cell gives the quietest buzzer in the table. ✓
Method. Read the table.
- Read the table. The three-cell buzzer is rated 5 out of 5.5
- Write the answer. 5
Check. Three cells give the loudest buzzer. ✓
Method. Read the table.
- Read the table. Two cells give 3.0 volts.3.0
- Write the answer. 3.0 volts
Check. 2 x 1.5 = 3.0. ✓
Method. Find the highest rating.
- Read the ratings. The highest rating is 5, for three cells.5
- Write the number. So three cells give the loudest buzzer.3
- Write the answer. 3
Check. The rating rises with the number of cells. ✓
Method. Subtract.
- Read the ratings. The ratings are 3 for two cells and 5 for three cells.3 and 5
- Subtract. The rise is 5 minus 3.5 - 3 = 2
- Write the answer. 2
Check. 3 + 2 = 5. ✓
Method. Read the table.
- Read the table. One cell gives 1.5 volts.1.5
- Write the answer. 1.5 volts
Check. One standard cell is 1.5 volts. ✓
Method. Compare the ratings.
- Read the ratings. Two cells give 3, and one cell gives 2.3 and 2
- Decide. Since 3 is more than 2, the answer is yes.yes
- Write the answer. yes
Check. More voltage makes a louder buzzer. ✓
Method. Compare the ratings for each pair.
- Pair 1 and 2. The ratings are 2 and 3, a difference of 1.3 - 2 = 1
- Pair 2 and 3. The ratings are 3 and 5, a difference of 2.5 - 3 = 2
- Write the answer. So the pair with a difference of 1 is 1 cell and 2 cells.1 and 2
- Write the answer. 1 and 2
Check. Only the first pair differs by 1 point. ✓
Method. Check the voltage.
- Check the table. Three cells give 4.5 volts, not 3 volts.4.5
- Decide. So Ruby is not right about the voltage.no
- Write the answer. no
Check. Each cell gives 1.5 volts. ✓
Method. Find the total voltage for three cells.
- Find the cells. Ali now has three cells.3 cells
- Multiply. Three cells give 3 x 1.5 volts.3 x 1.5 = 4.5
- Write the answer. 4.5 volts
Check. The rating 5 matches three cells in the table. ✓
Method. Think about the voltage.
- Think about the voltage. Adding a cell raises the total voltage by 1.5 volts.1.5
- Think about the current. A higher voltage makes more current flow, so the buzzer is louder.louder
- Write the answer. Accept any sentence that says adding a cell raises the total voltage, so more current flows and the buzzer is louder.
Check. More voltage gives a louder buzzer. ✓
Method. Think about comparing ratings.
- Think about the scale. The same scale of 1 to 5 must be used each time.same scale
- Think about the pattern. So the ratings can be compared fairly and the pattern can be checked.compared fairly
- Write the answer. Accept any sentence that says the same scale and the same judges keep the ratings comparable, so the pattern can be trusted.
Check. Fair comparison needs one scale. ✓