Electromagnetism

Electric Field

A region around a charged object where other charged objects experience a force.

Electric Potential

The amount of electrical potential energy per unit charge at a point in an electric field.

Electron Volt

A unit of energy equal to the amount of kinetic energy gained by a single electron accelerated through an electric potential difference of one volt.

Charge Separation in Clouds

The process where opposite charges accumulate in different parts of a cloud, creating a strong electric field.

Ionization

The process by which atoms are electrically charged either by gaining or losing electrons.

Electric Discharge

The release of stored electrical energy in the form of a spark or lightning when electric breakdown occurs.

Lightning Conductor

A device to protect buildings from lightning strikes by directing the electric current safely to the ground.

Electron Avalanche

A rapid multiplication of electrons resulting from ionization, leading to a conductive path in a high electric field.

Breakdown Voltage

The minimum electric field strength required to ionize a medium and create a conductive path.

Potential Difference

The difference in electric potential energy per unit charge between two points in an electric field.

Equipotential Surface

A surface on which the electric potential is the same at every point, meaning no work is done when moving along it.

Electric Charge

A physical quantity that describes the property of matter that causes it to experience a force in an electric field.

Charge Conservation

The principle that the total electric charge in a closed system remains constant.

Charge Quantization

The concept that electric charge is not continuous, but rather exists in discrete amounts, specifically integer multiples of the elementary charge.

Positive Charges

Types of charge that repel each other, typically associated with protons.

Negative Charges

Types of charge that repel each other, typically associated with electrons.

Like Charges

Charges that are of the same type (positive-positive or negative-negative) and repel each other.

Unlike Charges

Charges that are of opposite types (positive-negative) and attract each other.

Polar Molecule

A molecule that has a charge separation, having a slight positive charge at one end and a slight negative charge at the other.

Insulators

Materials in which electrons are tightly bound to atoms and cannot move freely, such as wood or rubber.

Conductors

Materials that contain electrons that are loosely bound to the atoms, allowing charge to move freely, such as copper and iron.

Charging by Contact

The process of transferring charge through direct physical contact between materials.

Charging by Induction

The process of inducing charges within an object without direct contact, usually involving the influence of a nearby charged object.

Electrical Polarization

The separation of charges within a neutral object when influenced by an external electric field.

Ion

An atom that has gained or lost one or more electrons, resulting in a positive or negative charge.

Static Electricity

Electricity that accumulates on the surface of objects, often resulting in attractive or repulsive forces.

Electric Potential

The electric potential energy per unit charge.

Electric Potential Energy (PE)

Energy stored due to the position of a charge in an electric field.

Electron Volt (eV)

The amount of work done when an electron is moved through a potential difference of 1 V.

Potential Difference (Voltage)

The difference in electric potential between two points, measured in volts (V).

Equipotential Lines

Lines along which the electric potential does not change, which are always perpendicular to electric field lines.

Scalar Quantity

A quantity that has only magnitude and no direction, such as electric potential.

Total Energy Conservation

Energy cannot be created or destroyed; it can only be transformed from one form to another.

Gravitational Potential Energy (GPE)

Energy stored due to an object's height above a reference point, depending on mass and height.

Unit of Electric Potential (Volt)

Defined as joule per coulomb (1 V = 1 J/C), representing the potential energy per unit charge.

Source of Electric Potential

Devices like batteries that maintain an electric potential difference between their terminals.

Kinetic Energy

The energy an object possesses due to its motion, which increases when a charge moves through an electric field.

Work Done by Electric Field

The energy transferred by the electric field when moving a charge against the electric potential.

Electric Field

A region around a charged object where other charged objects experience a force.

Force Field

A vector field that represents the magnitude and direction of forces acting at each point in space.

Electric Field Strength

The force experienced by a positive test charge per unit charge, measured in N/C.

Electric Field Lines

Imaginary lines that represent the direction and strength of an electric field; they start on positive charges and end on negative charges.

Superposition of Electric Fields

The principle that the resultant electric field at a point is the vector sum of the electric fields produced by individual charges.

Faraday Cage

A conductive enclosure that shields its interior from external electric fields.

Test Charge

A small charge used to probe the electric field at a point without affecting the field itself.

Vector Sum

The total electric field calculated from the individual contributions of multiple charge sources, considering their directions and magnitudes.

Gravitational Force Field

A gravitational field where the force on a mass is uniform, represented by the acceleration due to gravity, approximately 9.8 m/s².

Coulomb's Law

A formula that describes the force between two charged objects, which depends on the product of their charges and the distance between them.

Electric Charge

A physical quantity that can attract or repel other charges, existing in two types: positive and negative.

Charge Conservation

The principle that the net amount of electric charge produced in any process is zero; charge cannot be created or destroyed.

Charge Quantization

The concept that electric charge is not continuous; all charged objects are integer multiples of the elementary charge.

Static Electricity

An imbalance of electric charges within or on the surface of a material, leading to phenomena such as attraction or repulsion.

Conductors

Materials that allow electric charge to flow easily, such as metals.

Insulators

Materials that resist the flow of electric charge, holding electrons tightly bound to their atoms.

Electrical Polarization

The separation of charges within an object, where the object remains electrically neutral overall.

Coulomb's Law

The law specifying that the electric force between two charges is proportional to the product of the charges and inversely proportional to the square of the distance between them.

Electric Field

A field around a charged object where other charges experience a force, defined as the force per unit charge.

Electric Potential (Voltage)

The electric potential energy per unit charge, representing the work done to move a charge against an electric field.

Electron Volt (eV)

A unit of energy equal to the work done when an electron moves through a potential difference of 1 V.

Equipotential Lines

Lines along which the potential remains constant, being perpendicular to electric field lines.

Electric Discharge

A release of electricity, often seen as a visible spark or lightning, typically occurring when an electric field exceeds a critical strength.

Ammeter

A device for measuring the current in a component of a circuit by measuring the current passing through itself.

Ammeter Connection

The device must be connected in series with the component of interest to measure the current passing through it.

Ammeter Resistance

To avoid affecting the quantity it is measuring, its resistance must be very much less than the resistance in the circuit.

Voltmeter

A device for measuring the potential difference across a component of a circuit by measuring the potential difference between its own terminals.

Voltmeter Connection

The device must be connected in parallel with the component of interest.

Voltmeter Resistance

To avoid affecting the quantity it is measuring, its resistance must be very much greater than the resistance of the component.

Electric Shock Severity Factors

The severity depends on the magnitude of the current, the duration of the current flow, and the part of the body the current passes through.

Threshold of sensation

The effect produced by an electric current of $1\,mA$.

Maximum harmless current

The effect produced by an electric current of $5\,mA$.

Onset of sustained muscular contraction

An effect occurring at $10-20\,mA$ where the victim cannot let go for the duration of the shock and chest muscle contraction may stop breathing.

Onset of pain

The effect produced by an electric current of $50\,mA$.

Ventricular fibrillation

A condition that is often fatal, occurring at current levels of $100-300+\,mA$.

Onset of burns

An effect occurring at $300\,mA$ depending on the concentration of the current.

Defibrillation Current

A current of $6000\,mA$ ($6\,A$) which causes sustained ventricular contraction and respiratory paralysis that cease when the shock ends, allowing the heartbeat to return to normal.

"Thrown" backward response

An involuntary muscle contraction involving the extension of the legs and torso when exposed to electric current.

"Can’t let go" response

An effect where a victim is unable to release a wire because the hand muscles that close the fingers are stronger than those that open them.

Electric circuit

A continuous conducting path between the terminals of a battery through which charges can move.

Electric current ($I$)

The net amount of electric charge (\text{\Delta}Q) passing the full cross section at some point in a wire per unit time (\text{\Delta}t), defined by the formula I = \frac{\text{\Delta}Q}{\text{\Delta}t}.

Ampere ($A$)

The unit of current equal to one coulomb per second ($1\,C/s$).

Conventional current

A sign convention where moving charges are considered positive; the flow is opposite to the flow of actual electrons.

Electric shockwave (signal)

A rapidly propagating change in the electric field that moves through a wire close to the speed of light ($\sim 10^8\,m/s$).

Drift speed

The average speed at which actual charges move through a wire, which is approximately $10^{-4}\,m/s$.

Steady current properties

In a circuit with only one conducting path, the current at any instant is the same at every point because charge does not accumulate anywhere.

Direct Current (DC)

The flow of electric charge that moves in only one direction.

Alternating Current (AC)

The flow of electric charge that periodically reverses direction.

AC supply voltage advantage

Household electricity is AC because it is much easier to change the voltage of an AC supply compared to a DC supply.

Peak Voltage ($V_O$)

The maximum voltage value in an AC system, where the voltage varies mathematically between $+V_O$ and $-V_O$ according to the formula $V = V_o \tan(2\times \text{pi}\times f\times t)$, or more standardly written in the transcript as V = V_o \text{sin}(2\text{\pi}ft).

Standard Frequency ($f$) in Australia

The frequency at which the AC voltage varies, which is currently $50\,Hz$ (50 times per second).

Average Power ($P_{average}$) in AC

The product of voltage and current over time, expressed as $P_{average} = \frac{1}{2} V_o I_o$ when current and voltage are in phase.

Root Mean Square (rms) Voltage ($V_{RMS}$)

The effective or average voltage value defined as $V_{RMS} = \frac{V_o}{\sqrt{2}}$, which allows AC power formulas to resemble DC formulas.

Root Mean Square (rms) Current ($I_{RMS}$)

The effective or average current value defined as $I_{RMS} = \frac{I_o}{\sqrt{2}}$, used to calculate power transformation in a resistor.

Nominal Australian Domestic Supply

The standard domestic supply which has a $V_{RMS}$ of $240\,V$, corresponding to a peak voltage ($V_o$) of approximately $340\,V$.

AC Average Power Equations

The formulas for power in a resistor using rms values: $P_{average} = V_{rms} I_{rms} = I_{rms}^2 R = \frac{V_{rms}^2}{R}$.

Power Loss in Transmission ($P_{lost}$)

The power dissipated during transmission, calculated using the formula $P_{lost} = I^2 R_{wires}$.

Transmitted Current ($I$)

The current sent through lines, calculated as $I = \frac{P}{V}$; using a high voltage reduces this current to minimize power loss.

Resistance of Wires ($R_{wires}$)

The resistance defined by the property of the materials used, calculated as $R_{wires} = \frac{\rho L}{A}$; it is minimized by using thick wires with low resistivity.

Electric Power

The rate at which electrical energy is transformed into another form of energy, such as thermal energy in a heater or mechanical energy in a motor, defined by the formula $P = \frac{\text{energy transformed}}{\text{time}} = \frac{qV}{\Delta t}$.

$$P = VI$$

The expression for the power transformed in any device, representing the rate of energy transformation when the current passing through it is $I$ and the potential difference between its terminals is $V$.

Watt ($W$)

The unit of electric power, which is equivalent to one Joule per second ($J/s$).