Exam Study Notes on Waves, Sound and Electricity

Flashcards on Waves, Sound, Electricity, and Related Physics Concepts

Wave

A disturbance that propagates in space, transporting energy from one point to another without transporting matter.

Non-Mechanical Wave

A wave that does not require a medium for propagation (e.g., electromagnetic waves).

Mechanical Wave

A wave that requires a medium for propagation (e.g., sound).

Transverse Wave

Wave consisting of crests and troughs where particles vibrate at right angles to the direction of wave propagation.

Longitudinal Wave

Wave consisting of compressions and rarefactions where particles vibrate parallel to the direction of wave propagation.

Crest

The highest point of a transverse wave.

Trough

The lowest point of a transverse wave.

Compression

Section in a longitudinal wave where vibrating particles are closest together; pressure and density are high.

Rarefaction

Section in a longitudinal wave where vibrating particles are furthest apart; pressure and density are low.

Amplitude (A)

The maximum displacement of each particle from its mean position.

Wavelength (λ)

The distance between two nearest (adjacent) crests or troughs of a wave.

Frequency (n)

The number of vibrations per second; SI unit is hertz (Hz); depends on the source.

Time Period (T)

The time taken to complete one vibration.

Velocity (V)

The distance travelled by a wave in one second.

Sound

A form of energy that produces the sensation of hearing.

Vibration

A periodic back-and-forth motion of particles of an elastic body or medium about a central position (also named oscillation).

Loudness

Distinguishes between loud and feeble sounds; mainly depends on the amplitude of sound.

Pitch

Distinguishes between shriller and flatter sounds; mainly depends on the frequency of sound.

Echo

Reflected sound.

Acoustics

The study of the reflective properties of surfaces.

Reverberations

Garbled sound due to multiple reflections.

RADAR

Radio Detection And Ranging; consists of a transmitted radio signal and a receiver that detects echoes.

SONAR

Sound navigation ranging; uses sound propagation to navigate, communicate, or detect objects underwater.

Ultrasonic Waves

Frequencies above 20,000 Hz.

Infrasonic Waves

Frequencies below 20 Hz.

Resistance

A measure of the opposition to current flow in an electrical circuit; measured in ohms (Ω).

Ohm's Law

The voltage in a wire is equal to current multiplied by resistance; V=I·R.

Resistor

An electrical component that limits or regulates the flow of electrical current in an electronic circuit.

Series Circuit

A circuit where components are connected along a single path, so the same current flows through all components.

Parallel Circuit

A circuit where components are connected so that the current divides and flows through multiple paths.

Variable Resistor

A resistor which can have its resistance changed.

Rheostat

A variable resistor where the slider can be moved to change resistance.

Potentiometer

A variable resistor generally used in home electronic appliances for speed or volume control.

Live Wire

Usually red (old) or brown (new) and is at high voltage; carries electric current to the appliances.

Neutral Wire

Black (old) or light blue (new) and has voltage close to ground; completes the circuit.

Earth/Ground Wire

Green or yellow (old and new); provides safety against faults and current leaks.

Fuse

An electric/electronic or mechanical device used to protect circuits from over current, overload, and ensure circuit protection.

Short Circuit

Occurs when the live wire comes in contact with the neutral wire, resulting in a high amount of current flow.

Overloading

Occurs when a large amount of current flows through appliances.

Normal Short Circuit

Occurs when a wire carrying electrical current touches a live wire or other current-carrying wire.

Ground Fault

Occurs when a current-carrying wire touches the grounded part of the circuit.

Direct Current (DC)

The direction of the current of the voltage is always constant; a flow of charge that always flows in one direction.

Alternating Current (AC)

The direction of the current is always switched periodically and the voltage is also switched; a current that changes direction in time.

Mechanical Waves

Waves that require a medium (e.g., sound waves, water waves).

Electromagnetic Waves

Waves that do not require a medium (e.g., light, microwaves, X-rays).

Vibration

Is a movement about a fixed point.

Wavelength

The distance between two consecutive points in a longitudinal wave (compressions or rarefactions).

Transverse Wave

A moving wave consisting of oscillations occurring perpendicular to the direction of energy transfer.

Longitudinal Wave

A wave where particles vibrate parallel to the direction of propagation.

Frequency

Is directly proportional to pitch but inversely proportional to wavelength.

Pitch

The feature of sound that distinguishes shrill sound from a flat sound.

Loudness

A sound quality that allows distinguishing a noisy sound from a faint one; depends on the amplitude.

Time Period

The time taken to complete one vibration.

Amplitude

Maximum displacement from rest.

Wavelength

Distance between crests/troughs.

Frequency

Vibrations per second.

Time Period

Time for one full wave.

Wave Speed

Speed = frequency × wavelength.

Sound

A longitudinal mechanical wave.

Interference

Occurs when waves add up (constructive) or cancel (destructive).

Echo

Reflection of sound.

Oscilloscope

Used to display sound waves visually.

SONAR

Uses sound waves underwater.

RADAR

Uses radio waves to detect speed/distance of objects.

Current (I)

Flow of charge, I = Q/t.

Voltage (V)

Electric potential difference, V = IR.

Resistance (R)

Opposition to current.

Ohm’s Law

V = I × R.

Series Circuit

Current = same, Voltage = split, Resistance: R = R1 + R2 + R3.

Parallel Circuit

Voltage = same, Current = splits, Resistance: 1/R = 1/R1 + 1/R2 + 1/R3.

Resistor

Limits current.

Variable Resistor

Adjustable resistance (used in dimmers, radios).

Ammeter

Measures current (connected in series).

Voltmeter

Measures voltage (connected in parallel).

Live Wire

High voltage in.

Neutral Wire

Return path.

Earth Wire

Safety wire.

Earth Pin

Connects first for safety and directs stray current to the ground.

Fuse

Melts during overcurrent.

Static Electricity

Occurs when electrons transfer (e.g. by rubbing).

Conductors

Examples: Copper, metal.

Insulators

Examples: Rubber, plastic.

Semiconductors

Examples: Silicon, germanium.

Conventional Current

From + to –.

Electron Flow

From – to +.

Nebula

Cloud of gas/dust.

Volcano

A feature in Earth’s crust where molten rock is squeezed out onto the Earth’s surface.

Theia

Mars-sized protoplanet that struck Earth

Oceanic Plates

Consist of oceanic crust called sima (silicon and magnesium).

Continental Plates

Consist of continental crust called sial (silicon and aluminum).

Nebula

A giant cloud of dust and gas, primarily hydrogen and helium, in space.

Stellar Nursery

An area of outer space within a dense nebula where gas and dust are contracting, resulting in the formation of new stars.

Magma

Molten rock beneath the surface.

Lava

Molten rock when it erupts from a volcano.

Plate Tectonics

Convection currents drive the movement of Earth's rigid tectonic plates in the planet's fluid molten mantle.

Tectonics

The contintental drift hypotheis that the continents were assembled to form supercontinent Pangea and moved through time.

Earth Pin

Thicker and longer than other pins to ensure safety.

Earth Wire

Provides safety against faults and current leaks.

Neutral Wire

Completes the circuit by forming a path for current back to the mains; usually has approximately O V.

Live Wire

Carries electric current to the appliances; connected directly to the generators of the power station.