Physics Flashcards
charged particle
a particle with an electric charge e.g. ion, electron, proton
unit of elementary electrical charge
coulomb
conductors
the materials electricity (electrons) can flow through. e.g. copper, silver, gold, graphite, salt
insulators
the materials electricity (electrons) cannot flow through = static
static electricity
when two non-metal insulators are rubbed together, the friction allows electrons to be removed from one of the objects to the other, where they build up because the electrons don’t flow like in insulators.
static electricity is
potential energy. it does not move. it is stored.
charge in static electricity
one object becomes negatively charged, and the other becomes positively charged
static discharge
occurs when there is a loss of static electricity due to friction, conduction, or induction.
conduction
direct contact
induction
through an electric field (no direct contact)
voltage
the difference in potential energy across an energy source or circuit component. also called the potential difference.
unit for voltage
volts = V
current
the rate of coulombs flowing in the circuit. current is the number of coulombs per second
unit for current
amperes (amps) = A. 1A = 1 coulomb per second
current is
kinetic energy
direct current (DC)
electrons flow in the same direction in a wire
alternating current (AC)
electrons flow in different directions in a wire
resistance
when it is difficult for a current to flow through a circuit component. opposes the flow of current through a circuit component.
unit for resistance
ohm (Ω)
the effect longer wires have on resistance
increased resistance as the electrons travel further and lose energy
the effect wider wires have on resistance
decreased resistance as more electrons fit in a wide wire = less lost energy
voltage drop
a loss of potential energy when current flows through a circuit component. this is due to the transfer of electrical energy to other forms - light, sound, heat etc.
series circuit
when all the circuit components are in a line. the circuit forms a single loop.
current in a series circuit
the same current flows through every circuit component. the current measured at any point of the circuit will be the same value.
voltage in a series circuit
not necessarily the same over every circuit component. if two components have different resistances, there will be a larger voltage over the component with a larger resistance.
parallel circuits
composed of many branches/loops of wire
current in a parallel circuit
current is split between branches. current can flow down multiple paths and each electron can only travel down one path at a time. the current along each branch is determined by the resistance on the branches.
relationship between current and resistance in a parallel circuit
if one branch has a higher resistance than the other, it will have a lower current. electrons choose the path of least resistance.
voltage in a parallel circuit
voltage is the same along every branch. the voltage is not affected by the resistance of the components.
variable resistor
sliding contact can be adjusted so that the current passes through only a few coils of wire or many coils of wire. adjusts the value of current or voltage
ohm’s law
V = IR (voltage = current * resistance)
energy
the ability of an object to do work
work
when an object is making something happen. results from a force being applied that causes displacement of the object
energy transformation
when energy transforms between forms (mechanical, kinetic, thermal)
energy transfer
when energy is transferred between objects
energy can be transferred by
the movement of matter. wave motion between two places
wave motion
activity that carries energy from one place to another through a medium without actually moving any matter. a wave transports energy and not matter. no net movement of matter.
heat
the total of the potential and kinetic energy (internal energy) of the particles in a substance
thermal energy transfer
conduction, convection, radiation
conduction
the process by which heat energy is transmitted through collisions between neighbouring atoms or molecules.
convection
the transfer of thermal energy by the physical movement of fluid (liquid, gas, or plasma) from one location to another
radiation
the process by which energy, in the form of electromagnetic radiation, is emitted by a heated surface in all directions and travels directly to its point of absorption at the speed of light
electricity transfer
moving electrons transfer energy from the energy source to the user. electron flow = kinetic energy.
kinetic energy transfer
kinetic energy is transferred from one moving object to a stationary object via work. the energy moves from one object to another but stays in the same form.
energy transfer - sound
a form of kinetic energy. sound is transferred in a wave. when a speaker produces music, it vibrates back and forth. as it moves forward, it pushes on the closest air particle. the particle pushes the next and so on. as the speaker moves backward, it pulls the closest air particle back with it. this particle pulls the next air particle and so on.
sound requires
particles
mechanical wave requires
a medium to propagate and therefore cannot propagate through a vacuum
sound waves can travel through
air, water, some solids, but not through a vacuum
wavelength (λ)
the distance between any two crests or troughs
amplitude (a)
the maximum displacement of a particle from its mean (normal) position; i.e. height of a crest or depth of a trough
frequency (f)
the number of complete vibrations (or waves) per second. unit = hertz (Hz)
period (T)
the time taken to complete one vibration (or to produce one complete wave)
sound waves are produced by
a vibrating source
sound waves are
longitudinal waves made up of a series of compressions (high-pressure areas) and rarefactions (low-pressure areas)
transverse waves
particles move perpendicular (up and down) at right angles to the direction of the movement of the wave
longitudinal waves
particles move parallel (back and forward) in the same direction of the wave
the wave equation
v = f * λ and T = 1/f
electromagnetic radiation is a
transverse wave - no medium required
waves that do not require a medium
electromagnetic waves. e.g. radio, microwave, visible light, x-rays
waves that require a medium
mechanical waves. e.g. transverse, longitudinal
the speed of light
300,000 km/sec
how do different mediums affect the speed of light
light moves slower through denser materials because more particles get in its way. it is slowed down in transparent media such as air, water, and glass.
reflection
when light bounces off an object
specular reflection
if the surface is smooth and shiny, like glass, water or polished metal, the light will reflect at the same angle as it hit the surface
angle of incidence
the angle of reflection
the incident ray and reflected ray are
in the same plane as, but on opposite sides of, the normal
normal
the line drawn perpendicular to the reflecting surface at the point of incidence
refraction
bending of a light ray as it enters a new medium at an angle and its speed changes
a ray of light entering an optically more dense medium
it slows down and is refracted towards the normal
a ray of light entering an optically less dense medium
speeds up and refracts away from the normal
a ray that enters along the normal at 90° to the new medium
it will change speed but not direction
echo
the repetition of sound caused by the reflection of sound. produced when sound bounces off a hard surface
applications of echoes
sonar (SOund NAvigation And Ranging), radar (RAdio Detection And Ranging)
sound in different materials
travels fastest in a solid, slowest in a gas
high pitch sound
high frequency
loudness
the brain judges loudness by how much the eardrum vibrates
the greater the amplitude
the higher the sound
outer ear
ear flap (pinna), auditory canal, eardrum
ear flap (pinna)
collects sound waves
auditory canal
where air vibrates
eardrum
vibrates with sound waves, in contact with the hammer
middle ear
hammer, anvil, stirrup, eustachian tube, semi-circular canals
hammer, anvil, stirrup
pass vibrations to the oval window
eustachian tube
joins middle ear to mouth, keeps pressure in the ear same as that outside
semi-circular canals
assist in body balance
inner ear
cochlea, auditory nerve
cochlea
contains nerve endings that change vibrations into messages for the brain
auditory nerve
carries messages to the brain
how sound travels through the ear
Sound waves travel through the air and are collected by the pinna/ear flap. The sound waves then travel through the auditory canal and hit the eardrum, which vibrates. The vibration of the eardrum triggers the movement of the hammer, anvil, and stirrup, which amplify the sound waves. The sound waves then travel to the cochlea, which contains nerve endings that convert the sound waves into signals/messages for the brain. These signals then travel along the auditory nerve to the brain
electromagnetic spectrum sequence (longest to shortest wavelength)
radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, x-rays, gamma rays
radio waves
length of a football to the length of a football field. carry signals for television and cellular phones
microwaves
wavelengths can be measured in centimeters. longer microwaves (30cm) are used to heat food in a microwave oven.
infrared radiation
700 nanometers to 1 millimeter. the heat we feel from sunlight, or a warm sidewalk is infrared.
visible light
various frequencies of coloured light. colour is determined by the frequency. 400 to 700 nanometers
ultraviolet light
invisible to the human eye, insects can see them. used for security coding. 10 to 400 nanometers
x-rays
high penetration ability. 0.01 to 10 nanometers
gamma rays
smallest wavelength and the most energy. generated by radioactive atoms and nuclear explosions. less than 100 picometers.
