Which rule helps determine the direction of the magnetic field from current?

Which rule helps determine the direction of the magnetic field from current?

• A. Left hand rule
• B. Right hand rule
• C. Cross rule
• D. Thumb rule

Answer: (B)

The right-hand rule is used to find the direction of the magnetic field produced by an electric current. If you point your right thumb along the direction of the current in a straight wire, your fingers curl in the way the magnetic field circulates around the wire. So, the curling direction of your fingers represents the magnetic field lines around the conductor. In a coil or solenoid, if you curl your fingers in the direction of the current around the loops, your thumb then points in the direction of the magnetic field inside the coil. This rule specifically describes how current creates and directs the magnetic field, which is why it’s the correct choice here. The left-hand rule, by contrast, is about the force on a current in a magnetic field (the motor effect), not the field direction itself.

The right-hand rule is used to find the direction of the magnetic field produced by an electric current. If you point your right thumb along the direction of the current in a straight wire, your fingers curl in the way the magnetic field circulates around the wire. So, the curling direction of your fingers represents the magnetic field lines around the conductor. In a coil or solenoid, if you curl your fingers in the direction of the current around the loops, your thumb then points in the direction of the magnetic field inside the coil.

This rule specifically describes how current creates and directs the magnetic field, which is why it’s the correct choice here. The left-hand rule, by contrast, is about the force on a current in a magnetic field (the motor effect), not the field direction itself.