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Electricity: Circuits and their Components - Battery

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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A battery is defined as a combination of two or more electric cells connected together in a specific arrangement.

Circuit symbol representing a battery consisting of multiple cells.
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In a standard battery arrangement, the positive terminal (++) of one cell is connected to the negative terminal (−-) of the next cell. This is known as a series connection.

Diagram showing two cells connected in series to form a battery.
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Many devices like torches, transistors, and TV remote controls use batteries. In some devices, cells are placed side-by-side; however, they are still connected 'positive to negative' via a metal strip or wire.

Diagram of side-by-side cell placement with connecting wires.
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The total voltage of the battery is the sum of the voltages of the individual cells when connected in series.

Three cells in series showing additive voltage properties.

📐Formulae

Vtotal=V1+V2+V3+⋯+VnV_{total} = V_{1} + V_{2} + V_{3} + \dots + V_{n}

Number of Cells=VtotalVindividual cell\text{Number of Cells} = \frac{V_{total}}{V_{individual\ cell}}

💡Examples

Problem 1:

A student wants to make a battery using 44 cells, where each cell has a voltage of 1.5 V1.5\text{ V}. What will be the total voltage of the battery formed?

Solution:

The total voltage is calculated as: Vtotal=1.5 V+1.5 V+1.5 V+1.5 V=6.0 VV_{total} = 1.5\text{ V} + 1.5\text{ V} + 1.5\text{ V} + 1.5\text{ V} = 6.0\text{ V}

Explanation:

Since the cells are connected to form a battery, their individual voltages are added together to find the total voltage provided to the circuit.

Problem 2:

If a toy car requires a 9 V9\text{ V} battery to operate and you only have 1.5 V1.5\text{ V} cells, how many cells do you need to connect in series?

Solution:

Number of Cells=9 V1.5 V=6\text{Number of Cells} = \frac{9\text{ V}}{1.5\text{ V}} = 6

Explanation:

To achieve a specific higher voltage, we divide the required total voltage by the voltage of a single cell to determine the number of cells needed.

Problem 3:

A flashlight requires a total potential difference of 4.5 V4.5\text{ V}. If you are using cells of 1.5 V1.5\text{ V} each, draw the circuit diagram for the battery and calculate the number of cells used.

Circuit diagram of 3 cells connected in series for a 4.5V battery.

Solution:

Number of cells=4.5 V1.5 V=3\text{Number of cells} = \frac{4.5\text{ V}}{1.5\text{ V}} = 3

Explanation:

To achieve a higher voltage, cells must be connected in series. By dividing the total required voltage (4.5 V4.5\text{ V}) by the voltage of a single cell (1.5 V1.5\text{ V}), we determine that 33 cells are needed.

Problem 4:

A specific electronic toy uses a battery made of 22 cells connected in series. If each cell provides 1.2 V1.2\text{ V}, what is the output voltage appearing across the terminals AA and BB?

Circuit diagram showing two 1.2V cells in series between terminals A and B.

Solution:

Vtotal=1.2 V+1.2 V=2.4 VV_{total} = 1.2\text{ V} + 1.2\text{ V} = 2.4\text{ V}

Explanation:

When cells are connected in series, their individual voltages are added together to find the total voltage of the battery.