Chatper 4 | Electromagnetism

Luigi Galvani

Observed frog leg twitching when touched by two metals, proving bioelectricity.

Galvani’s Brass Hook

One metal used to stimulate the frog’s leg.

Galvani’s Iron Scalpel

The second metal used in the frog leg experiment.

Alessandro Volta

Scientist who developed early batteries.

Voltaic Pile

Precursor of the modern battery made of stacked copper and zinc plates.

Modern Battery

Uses a carbon rod as the positive terminal and a zinc can as the negative terminal.

Volt (V) – Unit of electric potential.

Right-Hand Rule

Determines the direction of the magnetic field around a current-carrying wire.

Solenoid

Long coil of wire that produces a magnetic field; stronger with more turns and higher current.

Electromagnet

Coil of wire wrapped around an iron core that produces an adjustable magnetic field.

Electromagnetic Induction

Generation of electric current by a changing magnetic field.

Source of Electromotive Force

Device that converts other forms of energy into electrical energy.

Hans Oersted (1820)

Demonstrated that electric current creates a magnetic field.

Michael Faraday

Observed induced current and formulated the first law of electromagnetic induction.

Faraday’s Law

Induced current depends on field strength, speed of field movement, angle to conductor, and number of coil turns.

Faraday’s Experiment

Changing magnetic field produced electric current measured by an ammeter.

Oersted’s Experiment

Moving charges produced a magnetic field.

Anode

Electrode where oxidation occurs.

Cathode

Electrode where reduction occurs.

Galvanic Cell

Converts chemical energy to electrical energy by spontaneous reactions.

Electrolytic Cell

Uses electrical energy to drive non-spontaneous reactions.

Electric Motor

Converts electrical energy into mechanical motion.

Commutator Rings

Devices that reverse current direction in a motor.

Induction Motor

Motor used to rotate the anode in X-ray tubes.

Electric Generator

Converts mechanical energy into electrical energy.

Transformer Law

Vs/Vp = Ns/Np, voltage ratio equals turns ratio.

Turns Ratio

Ratio of secondary coil turns to primary coil turns.

Closed-Core Transformer

Laminated iron core transformer that reduces eddy current losses and increases efficiency.

Eddy Current

Circulating current that opposes the inducing magnetic field and reduces efficiency.

Autotransformer

Single-winding transformer that varies voltage by self-induction and controls kVp.

Shell-Type Transformer

Transformer that confines magnetic field lines and is more efficient than closed-core.