Potential difference is created in an electric circuit due to a cell or battery.

Explanation:
When a cell or battery is connected to an electric circuit, it provides a source of electrical energy. This energy is converted into electrical potential energy, which is then used to create a potential difference or voltage across the circuit.

Cell or Battery as a Source of Electrical Energy:
- A cell or battery consists of chemical substances that undergo chemical reactions to produce electrical energy.
- In a cell, chemical reactions occur at the electrodes, creating a potential difference between them.
- This potential difference is maintained as long as the chemical reactions continue, providing a continuous supply of electrical energy.

Conversion of Chemical Energy to Electrical Potential Energy:
- Inside a cell or battery, chemical reactions cause electrons to be transferred from one electrode to another.
- This creates a surplus of electrons at one electrode (negative terminal) and a deficit of electrons at the other electrode (positive terminal).
- The surplus of electrons at the negative terminal creates a negative charge, while the deficit of electrons at the positive terminal creates a positive charge.
- This charge separation creates an electric potential difference between the two terminals.

Creation of Potential Difference in the Circuit:
- When the terminals of a cell or battery are connected to an electric circuit, the potential difference is established.
- The surplus of electrons at the negative terminal repels electrons in the circuit, creating a flow of electrons from the negative terminal to the positive terminal.
- This flow of electrons is what we commonly refer to as an electric current.
- The potential difference created by the cell or battery provides the driving force for the electrons to flow through the circuit.

Conclusion:
In summary, a potential difference is created in an electric circuit due to a cell or battery. The chemical reactions inside the cell or battery convert chemical energy into electrical potential energy, which is then used to establish a potential difference across the circuit. This potential difference drives the flow of electrons and creates an electric current in the circuit.