Series and parallel circuits diagram for investigating potential difference in IGCSE physics.

Problem Overview:

The task involves investigating potential differences in both series circuits and parallel circuits. The goal is to record the potential difference (voltage) across each component (bulbs and cells) in the circuits and compare the readings. Based on these observations, we need to draw conclusions about how potential difference behaves in series and parallel circuits.

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Step 1: Series Circuits

#### Task Description:
- Construct the given series circuits.
- Record the potential difference for each blank circle (across each bulb and cell).
- Add up the readings for the bulbs and compare them with the reading for the cells.
- Observe any patterns or relationships.

#### Key Concepts for Series Circuits:
1. Potential Difference (Voltage): In a series circuit, the total voltage supplied by the battery (or cells) is divided among the components (bulbs).
2. Kirchhoff's Voltage Law: The sum of the potential differences across all components in a closed loop equals the total voltage supplied by the source.

#### Observations and Solution:
- For a series circuit, the potential difference across each bulb will be less than the total voltage of the cells because the voltage is shared among the bulbs.
- When you add up the potential differences across all the bulbs, the total should equal the voltage of the cells (assuming no energy loss in the wires).

#### Example Calculation:
Suppose:
- Total voltage of the cells = 6 V.
- Circuit has 3 bulbs.
- Potential difference across each bulb = 2 V.

Then:
- Sum of potential differences across bulbs = \( 2 \, \text{V} + 2 \, \text{V} + 2 \, \text{V} = 6 \, \text{V} \).
- This matches the total voltage of the cells.

#### Conclusion for Series Circuits:
In a series circuit:
- The potential difference across each component is less than the total voltage of the cells.
- The sum of the potential differences across all components equals the total voltage of the cells.

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Step 2: Parallel Circuits

#### Task Description:
- Construct the given parallel circuits.
- Record the potential difference for each blank circle (across each bulb and cell).
- Compare the readings for the bulbs with the reading for the cells.
- Observe any patterns or relationships.

#### Key Concepts for Parallel Circuits:
1. Potential Difference (Voltage): In a parallel circuit, the potential difference across each branch is the same as the voltage supplied by the source.
2. Current Division: Current divides among the branches, but the voltage remains constant across all branches.

#### Observations and Solution:
- For a parallel circuit, the potential difference across each bulb is equal to the voltage of the cells because the voltage is the same across all branches.
- The readings for the bulbs will match the voltage of the cells.

#### Example Calculation:
Suppose:
- Total voltage of the cells = 6 V.
- Circuit has 3 bulbs connected in parallel.

Then:
- Potential difference across each bulb = 6 V (same as the cells).
- All bulbs will have the same voltage reading.

#### Conclusion for Parallel Circuits:
In a parallel circuit:
- The potential difference across each component is equal to the voltage of the cells.
- The voltage is the same across all branches.

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Final Answer:

- Series Circuits: The sum of the potential differences across all components equals the total voltage of the cells.
- Parallel Circuits: The potential difference across each component is equal to the voltage of the cells.

\[
\boxed{\text{In series circuits, the sum of voltages across components equals the total voltage. In parallel circuits, the voltage across each component equals the total voltage.}}
\]