Magnetism & Current-Carrying Conductors – Lecture Review

Set of key vocabulary flashcards covering fundamental definitions and principles related to magnetic fields, forces on charges and current-carrying conductors, loop torque, and practical measuring devices mentioned in the lecture notes.

Magnetic Field (B)

A region of space where a moving charge or current-carrying conductor experiences a magnetic force; measured in teslas (T).

Lorentz Force

The total force on a charged particle moving in electric and magnetic fields; for magnetic part only: F = q v B sinθ.

Force on a Straight Conductor

Given by F = I L B sinθ, where I is current, L is length in field, and θ is the angle between L and B.

Right-Hand Rule

Mnemonic to find direction of magnetic force: point fingers in velocity (or current) direction, curl toward B; thumb gives force on positive charge (or conventional current).

Torque on a Current Loop

τ = N I A B sinθ; causes rotation of a loop in a magnetic field unless its magnetic moment is parallel to B.

Magnetic Moment (μ)

Vector quantity N I A pointing perpendicular to the loop’s plane; interacts with B to produce torque.

Zero-Torque Orientation

Occurs when the loop’s magnetic moment is parallel or antiparallel to the external magnetic field (μ ‖ B).

Solenoid

A long coil of wire producing a nearly uniform magnetic field inside when current flows.

Magnetic North Pole

End of a magnet that seeks Earth’s geographic North; physically a magnetic south pole of Earth.

Geographic North Pole

Northern point of Earth’s rotational axis; corresponds to Earth’s magnetic south pole beneath it.

Uniform Magnetic Field

A magnetic field with constant magnitude and direction throughout a region, often represented by equally spaced parallel lines.

Centripetal Force in B-Field

For a charge moving perpendicular to B, magnetic force provides centripetal force: q v B = m v² / r.

Alternating Current (AC)

Current that periodically reverses direction; in galvanometers it produces deflection first one way then the opposite.

Direct Current (DC)

Current that flows in one direction only; produces steady deflection in a galvanometer.

Galvanometer

Sensitive device that detects and measures small electric currents via needle deflection in a magnetic field.

Compass Needle

Small permanent magnet free to rotate; aligns so its north-seeking end points toward Earth’s magnetic north (geographic north).

Electron Motion vs. Compass

An electron moving east creates a magnetic field whose north-seeking direction is determined by the right-hand rule, influencing nearby compass needles.

Current Loop Orientation

To prevent rotation, align the loop’s plane perpendicular to B so that μ is parallel to B.

Deflection Direction (+/-)

In a magnetic field, positive charges (or conventional current) deflect according to the right-hand rule; negative charges deflect opposite.

Magnetic Force vs. Centripetal

In circular motion of a charge within B, magnetic force equals required centripetal force, allowing determination of velocity, radius, or mass.