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An Introduction to Electricity and Magnetism – Vocabulary flashcards
Section I: Electricity
Overview: Building block of matter is the atom; atoms are the smallest unit of matter that cannot be chemically broken down; atoms combine to form molecules and compounds; matter around us (including the human body) is made of atoms.
Atom vs element: An atom is the smallest unit of matter; An element is a substance consisting of only one type of atom; The number of protons determines the element.
The Periodic Table lists all known chemical elements; each element is a different type of atom.
Electric Charge and the Atom:
Electric charge is a basic property causing forces in an electric field; charges can be positive (protons) or negative (electrons); neutrons have zero charge.
In an atom:
Protons: positively charged, located in the nucleus.
Neutrons: neutral, located in the nucleus.
Electrons: negatively charged, orbit the nucleus.
Opposite charges attract; like charges repel; neutrons neither attract nor repel.
In an atom, electrons are attracted to protons in the nucleus; this attraction keeps electrons orbiting the nucleus.
Most atoms have equal numbers of protons and electrons, offsetting to give zero net charge.
Mass and Motion in Atoms:
Protons and neutrons are much more massive than electrons; electrons move rapidly around the nucleus.
The movement of electrons is a source of electricity.
Four Fundamental Forces (brief):
Gravitational force: attraction between masses; depends on masses and distance.
Electromagnetic force: force between charged particles; holds electrons around nucleus.
Strong nuclear force: holds protons and neutrons together in the nucleus.
Weak nuclear force: transforms particles and is involved in radioactive decay.
Fundamental Force of Electricity: Coulomb’s Force
Electromagnetic force between two charged particles; strength depends on each particle’s charge and the distance between them.
As distance increases, the force weakens: inverse-square relationship (conceptual).
Electric Fields
An object with electric charge generates an electric field around it.
If a second charged object enters this field, it experiences a force (F) that depends on the charge of the second object and field strength.
An electric field has both magnitude and direction; field strength typically decreases with distance from the charge.
Field direction depends on attraction vs. repulsion; field lines point away from positive charges and toward negative charges.
Electric Field Lines (model):
From a positively charged object, lines radiate outward.
From a negatively charged object, lines point inward toward the object.
Conductors and Insulators
Conductors: allow easy flow of electrons (e.g., copper, silver, aluminum).
Insulators: resist electron flow (e.g., rubber, glass, plastic).
Vocabulary Review (key terms):
insulator, electric charge, neutron, atom, vector, electron, nucleus, conductor, element, electric field, gravitational force, proton
Using the Periodic Table (concepts tested):
Elements are identified by the number of protons in the nucleus (atomic number).
Examples: symbols and names as given (e.g., Fe, He, K, Ba; W, Co, Al, Cu).
Atomic number represents the number of protons; in a neutral atom, electrons equal protons.
Example answers from the exercise:
1a) iron: Fe, helium: He, potassium: K, barium: Ba
2a) W, Co, Al, Cu
3) The atomic number = number of protons.
4) Calcium (Ca) has 20 protons.
5) If carbon has 6 protons, it has 6 electrons (in a neutral atom).
6) The smallest number of protons among listed elements is 1 (Hydrogen).
Determine the Electric Charge (concept):
Objects can have positive, negative, or no net charge; interactions depend on the charge signs (like charges repel, opposite charges attract).
Example reasoning from the exercise: like charges repel; opposite charges attract (A–E-type pair interactions).
Electricity Quiz (conceptual focus):
Particles: like charges repel; opposite charges attract.
Coulomb’s Law relates charge magnitudes and distance to the force.
How electric force varies with distance: force increases as charges come closer; decreases with distance.
Protons and electrons: pros and cons; electrons around a nucleus; charge magnitudes are typically elementary charges.
Common sense about conductors vs insulators; electric fields and charges influence material behavior.
Circuit fundamentals (lead-in to Section II):
Electric current is the flow of electric charges (electrons) through a conductor.
A circuit is a closed loop that allows current to flow continuously.
Voltage is the electric force that causes electrons to flow; it is the potential difference between two points.
Resistance is how much a material impedes current; measured in ohms (Ω).
Ohm’s Law: I = rac{V}{R} where I is current (A), V is voltage (V), and R is resistance (Ω).
Conductive vs insulating materials: low resistance vs high resistance.
Storing Electric Charge and Capacitors (concepts tied to Section II):
Capacitors store electrical energy by accumulating charge on two conductive plates separated by an insulator (dielectric).
The dielectric between plates increases the amount of charge the capacitor can store.
Practical link to real-world systems: batteries, capacitors, and basic circuits underpin how power is delivered and controlled in everyday devices.
Section II: Circuits
Overview: Energy and its forms (kinetic, potential, thermal, gravitational, electric potential) and the laws of thermodynamics.
Energy (E) is measured in Joules (J) and can be transferred but not created/destroyed in an isolated system.
Three laws of thermodynamics (high-level):
1st law: conservation of energy — energy cannot be created or destroyed, only transferred.
2nd law: energy transfer is not 100% efficient; some energy becomes waste heat.
3rd law: as temperature approaches absolute zero, entropy approaches a constant value; absolute zero cannot be reached.
Electric Current and Electric Circuits
Electric current: flow of electric charges (electrons) through a conductor.
Circuit: a closed loop that provides a path for current to flow continuously.
Voltage and Electric Current (practical definitions):
Voltage (V): electric force that causes electrons to flow; measures potential difference between two points.
Current (I): flow rate of charge; measured in amperes (A) or coulombs per second (C/s).
Resistance (R): opposition to current; measured in ohms (Ω).
Ohm’s Law (reiterated): I = rac{V}{R}
Types of Circuits
Series circuit: all components connected in a single loop; current is the same through all components; adding loads reduces overall current; if one part breaks, the entire circuit stops.
Example: a string of mini lights; if one bulb goes out, the entire string darkens.
Parallel circuit: multiple paths for current; each pathway can be on/off independently; a break in one path does not stop current in others; home wiring is typically parallel.
Power Up: Batteries
A battery has two terminals: a positive and a negative terminal.
Separation of charges creates an electric field and voltage.
A chemical reaction inside the battery pushes charges through the circuit, creating current to power loads (lights, devices).
Storing Electric Charge
Capacitors store electric energy by accumulating charge on two conductive plates separated by an insulator.
A dielectric between plates increases the stored charge capacity of the capacitor.
Vocabulary Review (Section II):
ampere, battery, electric circuit, electric current, electric potential energy, gravitational potential energy, kinetic energy, Ohm’s law, parallel circuit, resistance, series circuit, voltage, etc.
Label the Electric Circuit (concepts to recall):
Circuit 1: series circuit; circuit is open (switch not connected); lightbulb will not light; closing the switch completes the circuit.
Circuit 2: series circuit; circuit is closed; if the bottom wire is cut, both lightbulbs go out (a break stops current throughout the loop).
Circuit 3: parallel circuit; circuit is closed; if a wire is cut in one branch, only that branch turns off while other branches stay lit.
True/False Highlights (Section II):
Kinetic energy is energy of motion: True.
Electric potential difference (voltage) is the energy difference between two points: True.
A battery has two positive terminals: False (one positive and one negative).
Voltage is the force that allows electric current to flow: True.
A lightbulb turns potential energy into electrical energy: False (it converts electrical energy into light and thermal energy).
A switch is a resistor: False (a switch opens/closes a circuit; a resistor adds resistance).
A house is wired with series circuits: False (usually parallel for independent operation).
A capacitor can store charge: True.
A dielectric between capacitor plates decreases the charge stored: False (it increases storage capability).
Ohm’s law shows the relationship between current, voltage, and resistance: True.
The conservation of energy means energy cannot be gained or lost: True (understood as conserved in a closed system).
A material with high resistance will increase the current: False (it decreases current).
Fill-in-the-Blank Highlights (Section II):
energy cannot be created or destroyed; even in electrical contexts, energy is conserved.
A battery maintains voltage by separating charges.
When a circuit is completed (battery connected with wire), charge flows; charges move to neutralize opposite charges.
An electric circuit is a closed loop that continuously allows current to flow.
A capacitor consists of two conductors separated by a dielectric.
Conductive materials generally have low resistance; insulating materials have high resistance.
A capacitor is used for quick bursts of current (e.g., camera flash).
You can increase a capacitor’s charge storage with a dielectric between plates.
Insulating materials generally have high resistance.
A dielectric is a material placed between the two plates in a capacitor.
Section III: Magnetism
Overview of Magnetism
Magnetism is a force associated with magnets; it exhibits two opposite poles: north and south.
Opposite poles attract; like poles repel.
Unlike electricity, there are no single charged particles that are monopoles in magnetism.
The fundamental unit of magnetism is the magnetic dipole (a north and a south pole together).
Magnetic Fields and Materials
Magnetic fields are created by moving electric charges.
All matter is made of atoms; electrons are charged and in motion, producing tiny magnetic fields around atoms.
Ferromagnetic materials (e.g., iron, nickel) can become permanent magnets when exposed to a strong magnetic field; their atoms line up and stay aligned.
Paramagnetic materials can be magnetized in the presence of a strong magnetic field but lose magnetism when the field is removed (e.g., paperclips can be magnetized briefly near a strong field).
Earth’s Magnetic Field
Generated by molten iron in Earth’s core and rotation of the planet; magnetic south pole is near the Arctic; magnetic north pole near the Antarctic.
Magnetic Field Lines and Compass
Field lines emerge from the magnet’s north pole and terminate at the south pole; lines form closed loops.
A compass aligns with the magnetic field, indicating direction.
Right-Hand Rule (for moving charges and magnets)
To determine direction around a current-carrying wire: use the right-hand rule; the index finger points in current direction, the curling of fingers shows the magnetic field, the thumb shows the force on a moving charge.
Solenoids and Magnetic Fields
A straight wire creates circular magnetic fields; when the wire is coiled into a solenoid, the field resembles that of a bar magnet with a defined north and south pole.
Faraday’s Law (Electromagnetic Induction)
Moving a magnet near a coil of wire or moving a coil near a magnet induces current in the wire.
The induced current increases with the rate of change of the magnetic field; stops when motion stops.
Power at Home and Transformers
Power plants generate electricity and use transformers to step voltage up or down for long-distance transmission; transformers have two coils on a magnetic core; AC produces a changing magnetic field that induces voltage in the secondary coil.
Inductors help smooth out changes in electricity.
Practical Rule: Right-Hand Rule Summary
Index finger: direction of current (positive charges); middle = direction of magnetic field; thumb = direction of magnetic force on moving charges.
Magnetism Exercises and Concepts
Vocab Review and True/False sections reinforce terms like alternating current, direct current, Faraday’s law, solenoid, ferromagnetic, paramagnetic, magnetic dipole, magnetic field, magnetic force, compass, inductors, and generators.
Magnetism Quiz (conceptual highlights):
Common misconceptions addressed (e.g., a magnet has two poles; magnetic monopoles do not exist in simple magnets).
Earth’s magnetic field generation, alignment of freely suspended magnets, and the effect of pole interactions.
Directionality of magnetic fields around current-carrying wires and around magnets.
The role of ferromagnetic vs paramagnetic materials in magnetism.
Section IV: Electromagnetic Waves
Overview: Light is an electromagnetic (EM) wave; EM waves are generated by oscillating electric and magnetic fields; visible color corresponds to different frequencies/wavelengths.
Wave Basics
Wave properties: wavelength (distance between crests), frequency (how many waves per second), amplitude (max displacement from rest).
Types of waves:
Transverse waves: vibration perpendicular to direction of travel.
Longitudinal waves: vibration parallel to direction of travel.
Electromagnetic Spectrum
EM waves cover a spectrum from radio waves (long wavelengths) to gamma rays (short wavelengths) with microwaves, infrared, visible light, ultraviolet, X-rays in between.
Creating Electromagnetic Waves
An EM wave is produced when an electric field oscillates up and down while a magnetic field oscillates side to side; the two fields are perpendicular to each other and to the direction of travel.
Applications of EM Waves
EM waves are used in radios, polarized glass, satellite signals, television and phone screens, LED lighting, solar panels, etc.
EM Waves Quiz (conceptual focus):
Understanding that EM waves can travel through space (vacuum) and carry energy.
Recognition of the spectrum categories and which frequencies/wavelengths correspond to which kinds of waves.
Basic comprehension of wave properties: frequency, wavelength, amplitude, and speed of EM waves (speed in vacuum is the speed of light, c).
Additional notes on equations and constants (relevant to the sections above):
Coulomb’s Law (conceptual form): the force between two point charges is inversely proportional to the square of the distance between them and proportional to the product of the charges:
F = k rac{|q1 q2|}{r^2}
Electric field due to a point charge: | extbf{E}| = k rac{|q|}{r^2}
Electric force on a test charge: extbf{F} = q extbf{E}
Ohm’s Law (circuitary): I = rac{V}{R}
Faraday’s Law of electromagnetic induction (conceptual form): the induced electromotive force (voltage) in a circuit is proportional to the rate of change of magnetic flux:
ext{EMF} = - rac{doldsymbol{ ext{Φ}}_B}{dt}
Transformer principle (concept): voltage change is proportional to the turns ratio of the coils:
rac{V_ ext{out}}{V_ ext{in}} = rac{N_ ext{secondary}}{N_ ext{primary}}
Quick connections to the real world and exam-style prompts (as in the transcript):
Distinguish between series and parallel circuits and predict behavior when a component is added or removed.
Identify and describe electric field direction around charges using field lines and the right-hand rule.
Explain how magnets and electricity interact (moving charges create magnetic fields; magnetic fields can induce current).
Describe the EM spectrum and practical uses of various EM waves (e.g., radio for communication; X-rays for imaging; infrared for heat).
Quick study tips drawn from the content:
Remember the directionality rules for electric fields and magnetic fields (field lines vs. force on charges).
Distinguish circuit types by current paths: series shares current; parallel shares voltage.
Use the right-hand rule to relate current, magnetic fields, and forces when dealing with wires and solenoids.
Recall that energy is conserved across transformations, and that capacitors store energy via charge separation (plates and dielectric).