A current is passed through a straight wire. The magnetic field established around it has its lines of forces

Options

A. circular
B. parabolic
C. elliptical
D. no fixed shape

Answer

To solve the question regarding the magnetic field established around a straight wire when a current is passed through it, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Concept**: When an electric current flows through a conductor, it generates a magnetic field around it. This phenomenon is a fundamental principle of electromagnetism.

2. **Visualizing the Wire**: Imagine a straight wire through which the current is flowing. Picture the wire as the center of a circle.

3. **Magnetic Field Lines**: The magnetic field lines around the wire are not straight; instead, they form concentric circles around the wire. This means that if you were to draw the magnetic field lines, they would look like circles centered on the wire.

4. **Direction of Magnetic Field**: To determine the direction of these magnetic field lines, we can use the right-hand thumb rule. According to this rule, if you point your thumb in the direction of the current (the flow of positive charge), your fingers will curl in the direction of the magnetic field lines.

5. **Conclusion**: Therefore, the magnetic field established around a straight wire when current passes through it has its lines of force in a circular pattern.

### Final Answer:
The magnetic field lines established around a straight wire when current is passed through it are **circular**.

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