FAA Aviation Mechanic General (AMG)Fundamentals of Electricity and ElectronicsMedium
A technician uses the right-hand rule for conventional current flow to determine the magnetic field direction around a straight current-carrying conductor. If the thumb points in the direction of current flow, what do the curled fingers represent?
- AThe direction of the magnetic field lines circling the conductor
- BThe direction of electron flow through the conductor
- CThe direction of the resulting force on the conductor
- DThe direction of the induced EMF in the conductor
Show answer & explanationAnswer & explanation
Correct answer: A. The direction of the magnetic field lines circling the conductor
When applying the right-hand rule for conventional current, the extended thumb represents current direction and the curled fingers show the direction the circular magnetic flux lines wrap around the conductor.
Why the other options are wrong
- B. Electron flow is opposite to conventional current and is represented by the left-hand rule instead.
- C. Force direction on a conductor in a field uses a separate rule (motor action), not this one.
- D. Induced EMF direction relates to generator action, not the static field around a current-carrying wire.
Right-Hand Rule (Conventional Current)
For a straight conductor, if the thumb points in the direction of conventional current flow, the curled fingers indicate the direction of the circular magnetic field around the wire.
- Used for conventional current (positive to negative)
- Left-hand rule used for electron flow theory
- Field lines form concentric circles around the conductor
Memory trick: 'Right hand, current flows' - thumb is current, fingers curl the field.