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Mechanical Waves/Sound
Sound is transported by means of longitudinal waves through air and various materials. Generally, the speed of sound rises as the temperature of air rises. When sound traveles at 343 m/s, the temperature is 20 degrees Celcius.
Frequency plays an integral role in determining the pitch (how high or low) of a sound: as frequency increases, so does pitch. Humans can hear pitches ranging from 20 Hz to 20,000 Hz (1 Hz - 1 cycle per second).
The intensity of a sound wave basically refers to how loud it is, something that is determined by the amplitude squared of the wave. Sound levels can be figured out using logarithms. The sound level beta, in decibels, is defined in terms of intensity:
B = 10log (I / Io)
Io is usually 10 ^-12 W/m2
Fundamental frequency is the frequency from which sound occurs (like when you strike a guitar string and it produces sound). The fundamental frequency equates to a wavelength that is twice the length of the string ( wavelength = 2L). Higher frequencies that strings vibrate at are identified as overtones, or harmonics, where one or more additional nodes exist. Each harmonic has a whole-number multiple of the fundamental for a frequency.
For wind instruments, sound vibrates through an open tube, with displacement antinodes at each end. The fundamental frequency equates to the wavelength that is twice the tube length (same as guitar string one). For a closed tube (where one end is closed), the fundamental corresponds to a wavelength four times the length of the tube.
When sound waves are produced from different sources, they interfere. When the sounds have different frequencies, beats happen at a frequency that is equal to the differenc in frequency of the two sources.
The change in the pitch of sound due to the motion of a source or the listener is known as the Doppeler Effect. When the source and listener approach each other, the pitch is higher; when the source and listener move away from each other, the pitch drops;
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Mechanical Waves/Sound
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Electric Potential and Electric Energy
change in potential energypotentialenergy as a joule per coloumbcoloum
Electric potential can be energy per charge, electric potential difference or voltage difference
the amount of work for moving a charge through an electric field at constant velocity is W = qdeltaV
equipotential lines run perpendicular to field lines at any point, and electric field lines always point in the direction of decreasing electric potential.
- a system consisting of a + charge and an electric field loses electric potentail energy when the charge moves in the direction of the field
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no energy is required to move a charged object along an equipotential surface ---- NO POTENTIAL DIFFERENCE
electric potential of lines depend on distance from sources potential. the lines are parallel to charged parallel plates, they are in the concentric circles around single charges.

- a system consisting of a + charge and an electric field loses electric potentail energy when the charge moves in the direction of the field
no energy is required to move a charged object along an equipotential surface ---- NO POTENTIAL DIFFERENCE
single charges.
E = electric potential
as + charge moves with E Ue drops
as - charge moves against E Ue drops
drop in Ue causes kinetic energy to increase
ΔVa capacitor is a charge storing devise, two conducting parallel plates
plates become equally and poositely charged when capacitor is in a circuit
the charge on each plate is related to volts given by Q=VC, where c is the capacitance. C = the permittivity of space(8.85e-12)A/d
ΔV = U / q = - ∫E•ds
Electric Potential Difference between two points in a uniform electric field: ΔV = -Ed
The electric potential created by a point charge at any distance r from the charge is: V = ke(q/r)

Electric potential energy is the change in potential energy as a certain charge is moved between two points
dividing the potential energy by the test charge gives electric potential, and has a value at every point in an electric field. Electric potential is abbreviated V. V is also a scalar quantity V = Pe/ q One volt is equal to one joule per coloumb
voltage difference
the amount of work for moving a charge through an electric field at constant velocity is W = qdeltaV
The electric field can be seen as a measure of the rate of change with position of the electric potential.
An electron volt is the energy a charge-field system gains or loses when a charge of magnitude e is moved through a potentail difference of 1V. --------- 1eV = 1.6x10^-19
electric potential.
- a system consisting of a + charge and an electric field loses electric potentail energy when the charge moves in the direction of the field
no energy is required to move a charged object along an equipotential surface ---- NO POTENTIAL DIFFERENCE
electric potential of lines depend on distance from sources potential. the lines are parallel to charged parallel plates, they are in the concentric circles around single charges.
E = electric potential
as + charge moves with E Ue drops
as - charge moves against E Ue drops
drop in Ue causes kinetic energy to increase
ΔV = U / q = - ∫E•ds
Electric Potential Difference between two points in a uniform electric field: ΔV = -Ed
The electric potential created by a point charge at any distance r from the charge is: V = ke(q/r)
Electric Potential Energy of a system of two charged particles: U = ke (q1q2)/ r12
The voltage difference across a resistor is given by: ΔV = IR
Power given off by a low resistor: P = IΔV = I2R = V2/R

Electric PotentialsPotential and Electric Energy
Electric potential energy is the change in potential energy as a certain charge is moved between two points
dividing the potential energy by the test charge gives electric potential, and has a value at every point in an electric field. Electric potential is abbreviated V. V is also a scalar quantity V = Pe/ q One volt is equal to one joule per coloumb
Electric potential can be energy per charge, electric potential difference or voltage difference
the amount of work for moving a charge through an electric field at constant velocity is W = qdeltaV
The electric field can be seen as a measure of the rate of change with position of the electric potential.
An electron volt is the energy a charge-field system gains or loses when a charge of magnitude e is moved through a potentail difference of 1V. --------- 1eV = 1.6x10^-19
equipotential lines run perpendicular to field lines at any point, and electric field lines always point in the direction of decreasing electric potential.

Lenz law says that the produced emf produces a current whose magnetic field opposes the original change in flux.
For a straight wire length of L moving with speed v perpendicular to a magnetic field Emf=BLv
Transformers