Electromagnetism: History, Fields, and Properties

• Electromagnetism is a physics branch connecting electrical charges and magnetic fields.
• It unifies these concepts into an interconnected theory explaining diverse scientific phenomena.
• The roots trace back to 600 BC with Thales and static electricity, significant advancements occurred in the 19th century with scientists like Ørsted, Faraday, and Maxwell.
• Terms covered are magnet properties, magnetization factors, electric field, and magnetic flux correlations.
• Electromagnetism deals with the electromagnetic force between electrically-charged particles and induces electromagnetic fields, like magnetic and electric fields, and light.
• Magnetic and electric fields are perpendicular in an electromagnetic wave, maintaining a transverse characteristic.
• Hans Christian Oersted invented electromagnetism.

Contributions of Oersted

• His experiment used a compass inside a solenoid (coiled wire).
• Initially, the compass pointed north, but when connected to a dry cell, the magnetic field deflected towards the south pole.
• Oersted hypothesized that a current-carrying wire is magnetic.

Properties of Magnets

• Magnets attract magnetic objects (metals).
• Nonmagnetic objects (plastics, clothes, paper) cannot be attracted.
• Pauli Exclusion Principle: an object's magnetic property is ferromagnetic, diamagnetic, or paramagnetic.

Ferromagnetic Objects

• These objects are totally magnetic.
• Iron 56Fe's valence electron structure is an example, with only one orbital filled with an opposite-spin electron, causing net magnetic moments when applying an external field.
• Ferromagnetic objects are classified as soft or hard.

Soft Ferromagnetic Objects

• These objects are easily magnetized and demagnetized.
• Silicon steels are an example.

Hard Ferromagnetic Objects

• These objects are not easily magnetized, but magnetization is permanent once magnetized.
• Alnico, an alloy of aluminum, nickel, and cobalt, is an example and is used in motors and loudspeakers.

Diamagnetic Objects

• These objects are totally unattractive to magnets.
• They have a completely-filled valence electron structure that cancels out any applied magnetic field, for example Helium.

Paramagnetic Objects

• These objects are partially magnetic
• Multiple factors like valency, temperature, and composition influence this.
• Nickel-59Ni with two unpaired electrons is paramagnetic because the unpaired electrons create a small net magnetic moment when a field is applied.

Factors of Demagnetization

• Heat demagnetizes objects by disrupting the magnetic domains and increasing atomic vibrations, exceeding the Curie temperature permanently.
• Size Difference between two magnets can cause demagnetization of the smaller one if a larger magnet overpowers its magnetic domains.
• Magnetization Force demagnetizes when an external magnetic field opposes the domain direction, hindering alignment.

Magnet Alignment

• Magnets align towards the Earth's geographical north by default.
• A current-carrying wire near a compass deflects the magnetic field south, according to Oersted's work.

Magnetic Poles

• Magnetic poles always occur in pairs.
• Cutting a bar magnet results in two new magnets, each with its own north and south poles.
• Magnetic monopoles are impossible to achieve.
• Like poles repel, unlike poles attract, similar to electric charges.

Electromagnets

• Electromagnets induce a magnetic field in a conductive material via flowing current.
• A copper wire initially diamagnetic becomes instantly magnetic in an electric field, explaining DC motor dynamics.
• Electromagnets can adjust the armature's rotational speed in devices like electric fans, consuming more power.
• Electromagnets are not permanent and rely on electric current and need careful selecting in DC motor experiments.

Electromagnet Components

• The four main parts of an electromagnet is the battery, wire, conductive nail, and solenoid.
• Battery supplies voltage/current.
• Wire conducts current and is a closed circuit.
• Conductive nail alters magnetic property upon current flow.
• Solenoid is the coiled wire and encloses the nail, ensuring current flow.

Magnetic Force

• Magnetic force (F) exerted on a current-carrying conductor is at an angle with magnetic field = F = B·I·L·sin θ.
• B = magnetic field strength in Tesla (T).
• I = current (wire).
• L = conductor length (solenoid).
• θ = angle (magnetic field direction/current).
• If all components are perpendicular, F = B·I· L.

Fleming’s Right-Hand Rule

• Fleming's right-hand rule helps locate components.

Increasing Electromagnet Strength

• Current increasing the number of solenoid loops and/or reduces a wire's resistance
• Magnetic Flux Density/Magnetic Strength increasing solenoid loops or use a longer the iron core.
• Magnetic Force/Magnetism increasing coils elevates voltage.
• Core Length impacts strength and activates the magnetic property.

Electromagnetic Induction

• Electromagnetic Induction induces/creates current in a conductor via a magnetic field.
• 19th Century discoveries like Oersted's (electric field creates magnetic field) led scientists to question the opposite.
• Joseph Henry and Michael Faraday had experiments proving magnetic fields induce electric currents.
• Measured with a galvanometer resulting in the invention of generators.

Induction Requirements

• Physical manipulations needed unlike Oersted's experiment.
• Magnetic fields induce electric fields only under specific conditions.
• Experiments induced an electromotive force, driving electrons to produce current.

Faraday and Henry’s Experiments

• Coil and a Bar Magnet involves a coil C, galvanometer G, and bar magnet.
• North pole inserted right deflects galvanometer.
• South pole insertion causes opposite deflection, deflection is permanent while the magnet always moves.
• Greater speed of moving magnets can impact deflection values.
• A Coil and Electromagnet is similar to previous experiment, though replaces bar magnet with a coil C2 connected to a dry cell.
• Coil C2 resembles a magnet.
• Moving coil closer deflects the galvanometer.
• Intensity depends on speed and coil C₂ to coil C₁ proximity.
• Second Experiment with Tapping Key the electromagnet had an attached tapping key K.
• Pressing the tapping key makes deflection values appear from the galvanometer.
• Removing the key makes values appear opposite the original.
• The abrupt change is a result of the tapping key.

Factors that Increase Deflection

• Applying the tapping key.
• Insert metal rod in the coils.
• Galvanometer deflections depended on certain factors.
• Lenz's Law governs these deflections.

Faraday’s Laws

• Faraday knew a changing magnetic field induces an electromotive force in a wire loop along with the specified factors.
• A conductor in a changing magnetic field induces an electromotive force, and in some cases induces current.

Current-Inducing Factors

• Proximity of the magnetic field.
• Velocity of approaching magnetic field, and a sudden change in the magnetic field.

Heinrich Lenz

• He described the direction relationship between induced electromotive force and currents
• Described the effect from electromagnetic induction which is referred to as Lenz’s Law
• Faraday’s Second Law was rewritten to contain Lenz’s original Sign Conventions.

Factors that Induce a Current

• Changing the area of the loop of wire and changing the angle between the loop and the magnetic.

Magnetic Flux

• Refers to the measure of the magnetic field is running through a loop of wire.
• ØB = B A cos θ and the terms are Wb/m2, measured in Tesla

Magnetic Flux Linkage

• In a coil involves multiplying a number of coils represented as N and is denoted by Ψ - that is dependent on the strength values of the variables in Formula 1.3.
• Lenz's Law is important in the analysis of both the direction of induced current and the changes in magnetic flux during electromagnetic induction for the amount of current.
• Fleming’s Right Hand Rule can be used to understand and measure values.

Doppler Effect of Light

• Applies the frequency of a waves perceived by eyes depend on a distance to light.
• Light reflects the colors green, red and blue, though when mixing it results in white light.
• Astronomers use the properties and the wave form from wavelengths used to detect objects going or getting near us.

Light Interactions

• Reflections of light refer to the transfer in energy or the change.
• This can be from materials and surfaces.

Three Types of Transparent Materials

• Opaque
• Translucent
• Transparent
• Reflections of two types are affected by the incident rates and the surface that the rates interact.

Types of Light

• Some are smooth
• Some are constructed with regular materials

Euclid’s Law of Reflection

• From the Father of Geometry - the angle of incidence is equal to the angle of reflection.
• Reflections always lay on the same plane.
• Snell’s Refraction Law mentions that light travels from medium to another.
• Refractive index is about how the light can slow down and also divide in that medium (which is calculated)

Light

• Bends and passes between the different mediums.
• It has something that measures how it can be calculated with formula 1 and 2.
• Light always will have the incident angle and refracted ray.

Light Aberration

• Light can cause light to create an alternating factor.
• Light creates bands and intense wavelength when passing through a gap.

Geometric Optics

• (Ray Optics) are branches of ray objects (which comes from ray objects)
• It analyzes objects that are microscopic.
• Mirrors are surfaces that are reflective

Mirrors

• Mirrors contain glass panes with reflective coatings

Types of Mirrors

• Plane Mirrors produce images like the original objects.
• Concave can focus light to points and is used in telescopes.
• Convex - these diverge from regular side points and can be used in car side mirrors.

Lenses

• These refract rays so an image can form:
• The lenses curve at various values.

Types of Lenses

• Convex - they have converging points and are thick at the center compared to its edges so light can travel to a focal point. Common for magnifying glasses.
• Concave - these use light rays away from points that they focus upon. Are much more thin compared to the edges or compared to the center itself.