PHYSCI - Electromagnetism

Electromagnetism

is the study of how electricity and magnetism interact. It explains how electric currents create magnetic fields and how changing magnetic fields generate electricity. This principle powers motors, generators, and wireless communication.

Benjamin Franklin (1706-1790)

was known to be the first to advance the concept of electricity. He proved that lightning is an electrical phenomenon that can be transferred and stored as electricity.

Benjamin Franklin

He also agreed in one-fluid theory of electricity, which states that electricity as an invisible fluid is present in all matter. He asserted that if a matter contains little amount of this fluid, it is negatively charged. Otherwise, the matter is positively charged. He named the positive charge as vitreous electricity and the negative charge as resinous electricity.

Charles Augustine De Coulomb

did an experiment on electric charges. His significant contribution is on the charges' interaction with each other. The law of charges states that like charges repel each other, while unlike charges attract each other. Using his torsion balance, he measured the force of attraction or repulsion based on how the wire was being twisted in his device. _______ proposed that the interaction of charges (attraction or repulsion) follows an inverse square law.

Coulomb’s Law

It states that the force is directly proportional to the product of the charges and inversely proportional to the square of the distance between them.

Electric Charge

• All ordinary matter contains both positive and negative charge.

• You do not usually notice the charge because most matter contains the exact same number of positive and negative charges.

• An object is electrically neutral when it has equal amounts of both types of charge.

Electric Charge

• Objects can lose or gain electric charges.

• A tiny imbalance in either positive or negative charge on an object is the cause of static electricity.

• ______ is a property of tiny particles in atoms. The unit of ______ is the coulomb (C). A

  quantity of charge should always be identified with a positive or a negative sign.

Net charge

_____ is also sometimes called excess charge because a charged object has an excess of either positive or negative charges.

Electric Forces

forces between the two kinds of charge can be observed with an electroscope.

Current

is the movement of electric charge through a substance.

Hans Oersted (1777-1851)

• discovered that electric current can create magnetic fields. This discovery of the relationship of electricity and magnetism led to the field of electromagnetism.

• discovered this relationship when he observed a compass needle redirected from magnetic north once he switched on and off the electric current of the battery. From this, he proposed that a current-carrying wire radiates magnetic field

Maxwell

• built upon the proposal of Michael Faraday by mathematically deriving that changing electric fields produced magnetic fields and in fact the two phenomena should be perceived as a single entity.

• This means oscillating electric fields would produce magnetic fields. A moving electric charge would thus produce a magnetic field due to the presence of its intrinsic electric field.

Andre Marie Ampere

• Inspired by the discovery of Oersted, _______ carried out experiments to verify the relationship of electricity and magnetism. He also investigated the effect if electric current to different types of conductors.

• One of his greatest discoveries was the attraction of two parallel wires carrying an electric current. He found out that the two wires attract each other if the currents flowing in them are in the same direction otherwise they repel each other.

Ampere’s Law

fundamental principle in electromagnetism that relates the magnetic field around a closed loop to the electric current passing through the loop. It explains that the magnetic field around an electric current is proportional to the electric current that serves as its source.

Biot - Savart’s Law

• Jean-Baptiste Biot (1774-1862) and Felix Savart (1791- 1841) also performed an experiment in 1820 about magnetic field produced by a current-carrying wire using the oscillation of a magnetic dipole

• The Biot-Savart Law is used to calculate the magnetic field (B) produced by a steady current element (infinitesimally small segment of current-carrying wire).

Michael Faraday

is often credited with what is known today as the ______’s lab of electromagnetic induction, which is the basic principle in the operation of motors, generators., transformers, and inductors. It states that in a closed circuit, the electromotive force is equal to the rate of change in magnetic flux with respect to the time elapsed.

Carl Friedrich Gauss

developed a consistent system of magnetic units, and with Wilhelm Weber built one of the first electromagnetic telegraphs. _____ laws describing magnetic and electric fluxes served as part of the foundation on which James Clerk Maxwell developed his famous equations and electromagnetic theory.

Gauss’s Law

_________ for electricity states that electric flux across any closed surface is proportional to the net electric charge enclosed in the surface divided by the permittivity of free space. _______ on magnetism states that the magnetic flux across any closed surface is zero.

Lorentz Force Law

is the force on a charged particle due to electric and magnetic fields. A charged particle in an electric field will always feel a force due to this field. It states that a charged particle moving in an electric and magnetic field experiences a force.