Which of the following correctly describes the magnetic field near a long straight wire? (a) The field consists of straight lines perpendicular to the wire. (b) The field consists of straight lines parallel to the wire. (c) The field consists of radial lines originating from the wire. (d) The field consists of concentric circles centred on the wire.

The right-hand rule is a simple method used to determine the direction of the magnetic field around a current-carrying conductor. Hold your right hand out with the thumb pointing in the direction of the electric current. Then curl your fingers around the wire. Your fingers will point in the direction of the magnetic field lines.

Imagine a long straight wire with current flowing through it. If we point our thumb along the direction of the current, our curled fingers will trace out the path of the magnetic field around the wire. This process is straightforward but highly useful.

The right-hand rule can help visualize the orientation of the magnetic field and is crucial in understanding how magnetic forces interact with electric currents.

Magnetic field lines are an essential concept to understand when studying the magnetic field around a wire. These lines are imaginary but offer a visual representation of the magnetic field.

Visualize that these lines form complete loops around the wire. They do not start or end at any point but rather continue in a circular path around the wire. This characteristic sets them apart from electric field lines, which originate and terminate on electric charges.

In the case of a long straight wire, the density of the magnetic field lines indicates the strength of the magnetic field. Closer to the wire, the lines are more densely packed, showing that the magnetic field is stronger there. As we move farther from the wire, the lines spread out, indicating a weaker magnetic field.

In the context of a magnetic field around a long straight wire, the magnetic field lines form concentric circles. These are circles that share the same center, centered around the wire.

To understand this better, picture the wire as the center of multiple rings. Each of these rings represents the path of the magnetic field at different distances from the wire. The inner rings are closer and indicate stronger magnetic fields, while the outer rings show weaker fields.

Seeing magnetic field lines as concentric circles helps eliminate misconceptions. It clarifies that the magnetic field does not project straight out, radiate outwards, or form parallel lines. Instead, these circular patterns best describe the magnetic field setup around a straight current-carrying wire.