Why does a long straight wire carry current produce a magnetic field?

📌 CONCEPT: A long straight wire carrying current produces a magnetic field due to the flow of charged particles, which generates a magnetic field around it.

📐 RULE / FORMULA: The direction of the magnetic field produced by a current-carrying wire can be determined using the right-hand rule, which states that if you point your thumb in the direction of the current, your fingers will curl in the direction of the magnetic field.

💡 WORKED EXAMPLE: Consider a current-carrying wire placed parallel to a cylindrical conductor. If the current flows in the same direction as the wire, the magnetic field will be directed inwards into the cylinder. If the current flows in the opposite direction, the magnetic field will be directed outwards from the cylinder. When the wire is moving past the cylinder, the direction of the magnetic field remains the same.

⚠️ COMMON MISTAKE: Students often confuse the direction of the magnetic field when the wire and cylinder are stationary versus when the wire is moving past the cylinder.