Glossary
Electric Motors
Devices that convert electrical energy into mechanical energy through the principle of magnetic torque on current-carrying loops. They utilize the force exerted on current loops in a magnetic field to produce continuous rotation.
Example:
From blenders to electric cars, electric motors are ubiquitous, all relying on the fundamental principle of magnetic torque to generate motion.
Forces Between Two Wires
The magnetic forces exerted on each other by two parallel current-carrying wires. Wires with currents in the same direction attract, while those with currents in opposite directions repel.
Example:
In a high-current transmission line, the forces between two wires carrying current in the same direction can be significant enough to cause them to visibly pull towards each other.
Magnetic Field from Current
The magnetic field generated by moving electric charges, such as those constituting an electric current. The field lines form concentric circles around a straight current-carrying wire.
Example:
When you turn on a light switch, the current flowing through the wires immediately creates a magnetic field from current around them, though it's usually too weak to notice.
Magnetic Field of a Long Straight Wire
The strength of the magnetic field at a specific distance from a long, straight wire carrying current. Its magnitude is inversely proportional to the distance from the wire.
Example:
Engineers designing sensitive electronic equipment must consider the magnetic field of a long straight wire from nearby power cables to prevent interference.
Magnetic Force on a Current-Carrying Wire
The force experienced by a wire carrying electric current when placed in an external magnetic field, resulting from the interaction between the moving charges in the wire and the field.
Example:
A straight wire carrying current to the right in a magnetic field pointing upwards will experience a magnetic force on a current-carrying wire pushing it out of the page.
Net Magnetic Force on a Closed Loop
The overall magnetic force acting on a complete circuit loop. In a uniform magnetic field, the net magnetic force on a closed loop is zero because forces on opposite sides cancel out.
Example:
Even though individual segments of a motor's armature experience forces, the net magnetic force on a closed loop of wire in a uniform field is zero, allowing it to rotate without translational movement.
Permeability of Free Space ($\mu_0$)
A fundamental physical constant representing the ability of a vacuum to permit magnetic field lines to pass through it. It is a key component in equations for magnetic fields.
Example:
The constant permeability of free space () is crucial for calculating the exact strength of a magnetic field generated by a current, much like permittivity is for electric fields.
Right-Hand Curl Rule (RHCR)
A mnemonic rule used to determine the direction of the magnetic field produced by a current-carrying wire. The thumb points in the direction of the current, and the curled fingers indicate the direction of the magnetic field lines.
Example:
To figure out which way a compass needle would point near a power line, you'd use the Right-Hand Curl Rule (RHCR), wrapping your fingers around the wire in the direction of the field.
Right-Hand Rule (RHR) for Wires
A mnemonic rule used to determine the direction of the magnetic force on a current-carrying wire. The thumb points in the direction of current, fingers point in the direction of the magnetic field, and the palm indicates the direction of the force.
Example:
To find the direction a speaker coil moves, you'd use the Right-Hand Rule (RHR) for Wires, aligning your thumb with the current and fingers with the magnetic field to see the resulting force.
Torque on a Current Loop
The rotational effect experienced by a current-carrying loop placed in a magnetic field, even if the net force is zero. This torque causes the loop to rotate.
Example:
The continuous rotation of an electric motor's armature is due to the torque on a current loop created by the interaction of its current with the motor's magnetic field.