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# Instrument Description The document describes the principles of magnetic fields and forces acting on currents. It provides a detailed explanation of the "Right-Hand Rule" and "Three-Finger Rule" to determine the direction of magnetic fields and forces caused by electric currents. ## 1. Magnetic...

# Instrument Description The document describes the principles of magnetic fields and forces acting on currents. It provides a detailed explanation of the "Right-Hand Rule" and "Three-Finger Rule" to determine the direction of magnetic fields and forces caused by electric currents. ## 1. Magnetic Field * **Magnetic Needles:** Magnetic needles align tangentially to the magnetic field lines, and these lines never intersect. Outside a magnet, the lines run from north pole to south pole. * **Right-Hand Rule:** Used to determine the direction of the magnetic field generated by current flow in a wire (i.e., a current-carrying conductor). The thumb represents the direction of the current, and the fingers of the right hand represent the direction of the magnetic field. This rule only applys to the direction of the field *around* a conductor. ## 2. Force on Currents The "Three-Finger Rule" is explained: * **Thumb:** Represents electric current direction. * **Index finger:** Represents the magnetic field direction. * **Middle finger:** Represents the direction of force acting on the current-carrying conductor. The direction of the force is perpendicular to both the current and the magnetic field. ## Coil (Spule) * **Inside a Coil:** The magnetic field is uniform. * **Outside a Coil:** The magnetic field is similar to that of a bar magnet. ## Lorentz Force * **Moving Charges:** A moving charge in a magnetic field experiences a force (Lorentz force). The direction and magnitude of the force, its strength, is determined using the "Three-Finger Rule" * **Forces on Conductors:** The overall force on a current-carrying conductor in a magnetic field is the vector sum of the forces on the individual moving charges within the conductor. **Notes:** * The force changes direction if the current direction or magnetic field direction is reversed. * The description of the forces applies to freely moving charges and current-carrying conductors in an external magnetic field, such as those inside a solenoid.