Transcript Semester Review for Physics

Semester Review for Physics
Chapter 16 – Electric Forces and
Fields
•
•
•
•
Section 1: Electric Charge
There are two kinds of electric charge: positive
and negative; likes repel, opposites attract
Electric charge is conserved
Charge is quantized; the magnitude of the
fundamental unit is the charge on a proton or
electron
Conductors and insulators can be charged by
contact. Conductors can be charged by
induction. Insulators can have a surface charge
induced by polarization.
Chapter 16 – Electric Forces and
Fields
Section 2 – Electric Force
• According to Coulomb’s Law, the electric force
between two charges is proportional to the
magnitude of each charge and inversely
proportional to the square of the distance
between the charges
• The electric force is a field force
• The resultant force on any charge is the vector
sum of the individual electric forces on that
charge
Chapter 16 – Electric Forces and
Fields
•
•
•
•
Section 3 – The Electric Field
An electric field exists in the region around a charged
object
Electric field strength depends on the magnitude of the
charge producing the field and the distance between that
charge and a point in the field
The direction of the electric field vector E is the direction
in which an electric force would act on a postive test
charge
Field lines are tangent to the electric field vector at any
point, and the number of lines is proportional to the
magnitude of the field strength
Chapter 17 – Electrical Energy and
Current
Section 1 – Eletric Potential
• Electrical potential energy is energy that a
charged object has because of its shape
and its position in an electric field
• Electric potential is electrical potential
energy divided by charge
• Only differences in electric potential
(potential differences) from one position to
another are useful in calculations
Chapter 17 – Electrical Energy and
Current
Section 2 - Capacitance
• The capacitance of an object is the magnitude of
the charge on each of a capacitor’s plates
divided by the potential difference between the
plates
• A capacitor is a device that is used to store
electrical potential energy. The potential energy
stored in a charged capacitor depends on the
charge and the potential difference between the
capacitor’s plates.
Chapter 17 – Electrical Energy and
Current
Section 3 – Current and Resistance
• Current is the rate of charge movement
• Resistance equals potential difference
divided by current
• Resistance depends on length, crosssectional area, temperature and material
Chapter 17 – Electrical Energy and
Current
•
•
•
•
Section 4 – Electric Power
In direct current, charges move in a single
direction; in alternating current, the direction of
charge movement continually alternates
Electric power is the rate of conversion of
electrical energy
The power dissipated by a resistor equals
current squared times resistance
Electric companies measure energy consumed
in kilowatt-hours
Chapter 18 – Circuits and Circuit
Elements
•
•
•
•
Section 1 – Schematic Diagrams and Circuits
Schematic diagrams use standardized symbols to
summarize the contents of electric circuits
A circuit is a set of electrical components connected so
that they provide one or more complete paths for the
movement of charges
Any device that transforms nonelectrical energy into
electrical energy, like a battery or generator, is a source
of emf
In the internal resistance of a battery is neglected, the
emf can be considered equal to the terminal voltage, the
potential difference across the source’s two terminals
Chapter 18 – Circuits and Circuit
Elements
•
•
•
•
Resistors in Series or in Parallel
Resistors in series have the same current
The equivalent resistance of a set of resistors
connected in series is the sum of the individual
resistances
The sum of currents in parallel resistors equals
the total current
The equivalent resistance of a set of resistors
connected in parallel is calculated using an
inverse relationship
Chapter 18 – Circuits and Circuit
Elements
Section 3 – Complex Resistor Combinations
• Many complex circuits can be understood
by isolating segments that are in series or
in parallel and simplifying them to their
equivalent resistances
Chapter 19 - Magnetism
•
•
•
•
Section 1 – Magnets and magnetic Fields
Like magnetic poles repel, opposites attract
A magnetic domain is a group of atoms whose magnetic
fields are aligned
The direction of any magnetic field is defined as the
directions the north pole of a magnet would point if
placed in the field. The magnetic field of a magnet points
from the north pole to the south pole
The magnetic north pole of Earth corresponds to the
geographic south pole and the magnetic south pole of
Earth corresponds to the geographic north pole
Chapter 19 - Magnetism
Section 2 – Magnetism from Electricity
• A magnetic field exists around any currentcarrying wire; the direction of the magnetic
field follows a circular path around the wire
• The magnetic field created by a solenoid
or coil is similar to the magnetic field of a
permanent magnet
Chapter 19 - Magnetism
Section 3 – Magnetic Force
• The direction of the force on a positive charge moving
through a magnetic field can be found by using the
alternate right hand rule
• A current-carrying wire in an external magnetic field
undergoes a magnetic force. The direction of the
magnetic force on the wire can be found by using the
alternate right hand rule
• Two parallel current-carrying wires exert on one another
forces that are equal in magnitude and opposite in
direction. If the currents are in the same direction, the
two wires attract one another. If the currents are in the
opposite direction, the two wires repel one another.
Chapter 20 – Electromagnetic
Induction
Section 1 – Electricity from Magnetism
• A change in magnetic flux in a conducting coil
induces and electric current in the coil. This is
called electromagnetic induction
• Lenz’s Law states that the magnetic field of an
induced current opposes the change that
caused it
• The magnitude of the induced emf can be
calculated using Faraday’s Law
Chapter 20 – Electromagnetic
Induction
Section 2 – Generators, Motors, and Mutual Inductance
• Generators use induction to convert mechanical energy
into electrical energy
• Motors use an arrangement similar to that of generators
to convert electrical energy into mechanical energy
• Mutual inductance is the process by which an emd is
induced in one circuit as a result of a changing current in
another nearby circuit
Chapter 20 – Electromagnetic
Induction
Section 3 – AC Circuits and Transformers
• Transformers change the emf of an alternating current in
an ac circuit.
Chapter 20 – Electromagnetic
Induction
Section 4 – Electromagnetic Waves
• Electromagnetic waves are transverse waves that are
traveling at the speed of light and are associated with
oscillating electric and magnetic fields.
• Electromagnetic waves transfer energy. The energy of
electromagnetic waves is stored in the waves’ electric
and magnetic fields.
• The electromagnetic spectrum has a wide variety of
applications and characteristics that cover a broad range
of wavelengths and frequencies.
Chapter 11 – Vibrations and Waves
•
•
•
•
Section 1 – Simple Harmonic Motion
In simple harmonic motion, restoring force is
proportional to displacement
A mass-spring system vibrates with SHM and
the spring force is given by Hooke’s Law
For small angles, a simple pendulum swings
with SHM
In SHM, restoring force and acceleration are
maximum at maximum displacement and speed
is maximum at equilibrium
Chapter 11 – Vibrations and Waves
Section 2 – Measuring SHM
• The period of a mass-spring system
depends only on the mass and spring
constant.
• The period of a simple pendulum only
depends on the string length and free-fall
acceleration.
• Frequency is the inverse of period
Chapter 11 – Vibrations and Waves
•
•
•
•
Section 3 – Properties of Waves
As a wave travels, the particles of the medium
vibrate around an equilibrium position
In a transverse wave, vibrations are
perpendicular to the direction of wave motion.
In a longitudinal wave, vibrations are parallel to
the direction of wave motion
Wave speed equals frequency times wavelength
Chapter 11 – Vibrations and Waves
Section 4 – Wave Interactions
• If two or more waves are moving through a
medium, the resultant wave is found by
adding the individual displacements
together point by point
• Standing waves are formed when two
waves that have the same frequency,
amplitude and wavelength travel in
opposite directions and interfere.
Chapter 12 - Sound
Section 1 – Sound Waves
• The frequency of a sound wave
determines its pitch
• The speed of sound depends on the
medium
• The relative motion between the source of
waves and an observer creates an
apparent frequency shift known as the
Doppler Effect
Chapter 12 - Sound
•
•
•
•
•
•
•
Section 2 – Sound Intensity and Resonance
The sound intensity of a spherical wave is the power per area
Sound intensity is inversely proportional to the square of the
distance from the source because the same energy is spread over a
larger area
Intensity and frequency determine which sounds are audible
Decibel level is a measure of relative intensity on a logarithmic
scale.
A given difference in decibels corresponds to a fixed difference in
perceived loudness
A forced vibration at the natural frequency produces resonance
The human ear transmits vibrations that cause nerve impulses. The
brain interprets these impulses as sounds of varying frequencies.
Chapter 12 - Sound
•
•
•
•
Section 3 - Harmonics
Harmonics are integral multiples of the
fundamental frequency
A vibrating string or pipe open at both
ends produces all harmonics
A pipe closed at one end produces only
odd harmonics
The number and intensity of harmonics
account for the sound quality of an
instrument, known as timbre
Chapter 13 – Light and Reflection
Section 1 – Characteristics of Light
• Light is electromagnetic radiation that
consists of oscillating electric and
magnetic fields with different wavelengths
• The frequency times the wavelength of EM
radiation equals c, the speed of light
• The brightness of light is inversely
proportional to the distance squared from
the light source
Chapter 13 – Light and Reflection
Section 2 – Flat Mirrors
• Light obeys the law of reflection, which
states that the incident and reflected
angels of light are identical
• Flat mirrors form virtual images that are
the same distance from the mirror’s
surface as the object is
Chapter 13 – Light and Reflection
Section 3 - Curved Mirrors
• The mirror equation relates object
distance, image distance and focal length
of a spherical mirror
• The magnification equation relates image
height or distance to object height or
distance
Chapter 13 – Light and Reflection
Section 4 – Color and Polarization
• Light can be linearly polarized by
transmission, reflection or scattering
Chapter 14 - Refraction
Section 1 - Refraction
• According to Snell’s Law, as a light ray travels
from one medium into another where its speed
is different, the light ray will change its direction
unless it travels along the normal
• When light passes from a medium with a smaller
index of refraction to one with a higher index of
refraction, the ray bends towards the normal. For
the opposite situation, the ray bends away from
the normal.
Chapter 14 - Refraction
Section 2 – Thin Lenses
• The image produced by a converging lens is real
and inverted when the object is outside the focal
length and virtual and upright when inside the
focal length. Diverging lenses always produce
upright, virtual images
• The location of an image created by a lens can
be found using either ray diagrams or the thin
lens equation
Chapter 14 - Refraction
Section 3 – Optical Phenomena
• Total internal reflection can occur when light
attempts to move from a material with a higher
index of refraction to one with a lower index of
refraction. If the angle of incidence of a ray is
greater than the critical angle, the ray is totally
reflected at the boundary
• Mirages and the visibility of the sun after it has
physically set are natural phenomena that can
be attributed to the refraction of light in Earth’s
atmosphere
Chapter 15 – Interference and
Diffraction
Section 1 - Interference
• Light waves with the same wavelength and constant
phase differences interfere with each other to produce
light and dark interference patterns
• In double-slit interference, the position of a bright fringe
require that the path difference between two interfering
point sources be equal to a whole number of
wavelengths
• In double-slit interference, the position of a dark fringe
require that the path difference between two interfering
point sources be equal to an odd number of half
wavelengths
Chapter 15 – Interference and
Diffraction
Section 2 - Diffraction
• Light waves form a diffraction pattern by passing
around an obstacle or bending through a slit and
interfering with each other
• The position of a maximum in a pattern created
by a diffraction grating depends on the
separation of the slits in the grating, the order of
the maximum and the wavelength of the light
Chapter 15 – Interference and
Diffraction
Section 3 - Lasers
• A laser is a device that transforms energy
into a beam of coherent monochromatic
light