what mathematical equation is used for a circuit to find i when you know p and r?

Electric Electric current , Electric Power , Electrical Voltage

Electricity and Electric Charge

The nigh common general formulas used in electric engineering

● Basic Formulas and Calculations ●

Relationship of the physical and electrical quantities (parameters)
Electric voltage V , amperage I , resistivity R , impedance Z , wattage and power P
Volt V , ampere A, resistance and impedance ohm Ω , and watt Westward

The nominal impedance Z = 4, 8, and 16 ohms (loudspeakers) is often assumed as resistance R .
Ohm's police equation (formula): Five = I × R and the power law equation (formula): P = I × V .
P = power, I or J = Latin: influare, international ampere, or intensity and R = resistance.
5 = voltage, electric potential divergence Δ V or E = electromotive strength (emf = voltage).

Enter whatever two known values and press "summate" to solve for the ii others. Delight, enter only 2 values.

The Formula Wheel of Electrical Applied science

V comes from "voltage" and Eastward from "electromotive force (emf)". E means as well energy, so we choose V .
Energy = voltage × charge. E = V × Q . Some similar amend to stick to E instead to Five , so do it. For R take Z .

The 12 nearly important Formulas:
Voltage V = I × R = P / I = √ ( P × R ) in volts Five          Electric current I = 5 / R = P / V = √ ( P / R ) in amperes A
Resistance R = Five / I = P / I ² = Five ² / P in ohms Ω     Power P = V × I = R × I ² = V ^two / R in watts W

See besides: The Formula Wheel of Acoustics (Audio)

Ability Formula 1 – Electrical power equation: Ability P = I × V = R × I two = V two ⁄ R  where ability P is in watts, voltage V is in volts and current I is in amperes (DC). If at that place is Air conditioning, look besides at the power gene PF = cos φ and φ = power factor angle (phase angle) between voltage and amperage.  Electric Energy is E = P × t − measured in watt-hours, or also in kWh. 1J = 1N × m = 1W × s Power Formula 2 – Mechanical ability equation: Power P = E ⁄ t where ability P is in watts, Power P = work / time ( Westward ⁄ t ). Energy East is in joules, and time t is in seconds. 1 W = 1 J/due south.  Ability = force multiplied by displacement divided by time P = F × due south / t or Power = force multiplied by speed (velocity) P = F × 5. Undistorted powerful sound is not plant in these formulas. Please, mind your ears! The eardrum and microphone diaphragms are really only moved by the waves of the sound force per unit area . That does not practice either the intensity, nor the power or the energy. If you lot are in the audio recording business, it is wise not to care much virtually the free energy, power and intensity every bit the crusade, care more well-nigh the effect of sound force per unit area p and audio pressure level at the ears and at the microphones and look at the corresponding audio voltage V ~ p ; see: Audio pressure level and Sound power − Effect and Cause  Very loud sounding speakers will have a lot of power, but better expect closer at the very of import efficiency of loudspeakers. This includes the typical question: How many decibels (dB) are really twice or iii times as loud?  There is actually no RMS power. The words "RMS power" are not right. There is a adding of power which is the multiplication of a RMS voltage and a RMS current. Watts RMS is meaningless. In fact, we use that term as an farthermost autograph for ability in watts calculated from measuring the RMS voltage. Delight, read here: Why there is no such affair as 'RMS watts' or 'watts RMS' and never has been.  "RMS" ability is a rather light-headed term which has gathered currency among audio people. Ability is the corporeality of energy that is converted to a unit of time. Expect to pay more when demanding higher ability.

Andr�-Marie Amp�re was a French physicist and mathematician.
The SI unit of measurement of electric current, the ampere, was named subsequently him.
Alessandro Giuseppe Antonio Anastasio Volta was an Italian physicist.
The SI unit of measurement of electrical voltage, the volt, was named after him.
Georg Simon Ohm was a German physicist and mathematician.
The SI unit of measurement of electric resistance, the ohm, was named after him.
James Watt was a Scottish inventor and mechanical engineer.
The SI unit of electric wattage (power), the watt, was named later him.

Power is like all energy sizes primarily a calculated value.

The discussion "power amplifier" is a misnomer – particularly in audio engineering. Voltage and current can be amplified. The strange term "ability amplifier" has go understood to mean an amplifier that is intended to drive a load such as a loudspeaker. We telephone call the product of current gain and voltage proceeds "power distension".

Tip: The electrical voltage triangle 5 = I × R (Ohm'south police VIR)
Please enter two values, the third value volition be calculated. The electric power triangle P = I × V (Power law PIV)
Delight enter ii values, the 3rd value will be calculated.

A magic triangle can be used to calculate all formulas easily. You lot hide with
a finger the value to exist calculated. The other two values prove then how to practise the calculation.

Calculations: Ohm's law - Ohm's magic triangle
Measurement of input impedance and output impedance

ALTERNATING  Electric current (AC) ~

V _l = line voltage (volts), V _p = phase voltage (volts), I _l = line current (amps), I _p = phase current (amps)
Z = impedance (ohms), P = power (watts), φ = power gene angle, VAR = volt-amperes (reactive)

Current (single phase): I = P / Five p×cos φ	Electric current (three phases): I = P / √iii V fifty×cos φ or I = P / three 5 p×cos φ
Power (single phase): P = 5 p×I p×cos φ	Power (3 phases): P = √3 5 l×I l×cos φ or P = √iii 5 p×I p×cos φ

Ability cistron PF = cos φ = R/(R2 + X2)^1/2 , φ = power factor angle. For the purely resistive circuit, PF = i (perfect).
The apparent power Due south is calculated co-ordinate to Pythagoras, the active power P and reactive power Q . South = √( P ² + Q ²)

DC power formulas
Voltage V in (V) calculation from current I in (A) and resistance R in (Ω):
V _(V) = I _(A) × R _(Ω)
The power P in (W) calculation from voltage V in (V) and current I in (A):
P _(W) = V _(V) × I _(A) = V ⁱⁱ _(V) / R _(Ω) = I ⁱⁱ _(A) � R _(Ω)

Air conditioning power formulas
The voltage V in volts (V) is equal to the electric current I in amps (A) times the impedance Z in ohms (Ω):
V _(V) = I _(A) � Z _((Ω) = (| I | × | Z |) and (θ _I + θ _Z)
The apparent power S in volt-amps (VA) is equal to the voltage V in volts (V) times the current I in amps (A):
S _(VA) = V ₍₅₎ � I _(A) = (| V | × | I |) and (θ _Five − θ _I)
The real power P in watts (W) is equal to the voltage V in volts (V) times current I in amps (A) times the
power gene (cos φ):
P _(W) = V ₍₅₎ × I _(A) × cos φ
The reactive power Q in volt-amps reactive (VAR) is equal to the voltage V in volts (Five) times the electric current I
in amps (A) time the sine of the complex power phase bending (φ):
Q _(VAR) = Five _(V) × I _(A) × sin φ
The power gene (FP) is equal to the absolute value of the cosine of the complex power phase angle (φ):
PF = | cos φ |

The true power factor and not the conventional 50/60 Hz displacement power factor

Electric Measurement Definitions
Quantity	Proper noun	Definition
frequency f	hertz (Hz)	1/s
strength F	newton (N)	kg·m/south²
pressure p	pascal (Pa) = N/yard²	kg/k·southward²
free energy E	work joule (J) = N·m	kg·m²/southward²
power P	watt (Due west) = J/southward	kg·m²/s³
electric charge Q	coulomb (C) = A·south	A·s
voltage Five	volt (Five)= W/A	kg·m²/A·s³
current I	ampere (A) = Q/southward	A
capacitance C	farad (F) = C/V = A·s/V = s/Ω	A²·s4/kg·yard²
inductance L	henry (H) = Wb/A = Five·due south/A	kg·g²/A²·s²
resistance R	ohm (Ω) = 5/A	kg·k²A²·south³
conductance G	siemens (Due south) = A/V	A²·s³/kg·m²
magnetic flux Φ	weber (Wb) = V·due south	kg·k²/A·southward²
flux density B	tesla (T) = Wb/m² = 5·s/g²	kg/A·south²

The menstruation of electric charge Q is referred to as an electric electric current I. The amount of accuse per unit time
is the change in electric current. A current flows at a abiding value I. during the time t , information technology transports
the charge Q = I × t. For a temporally abiding ability, the relationship between the charge and current:
I = Q / t or Q = I × t. Through this human relationship, the bones units of amps and 2nd the Coulomb in
International Organisation of Units is set. The Coulomb unit can be represented as one C = ane A × south.
Charge Q , (unit of measurement in ampere-hours Ah), discharge current I , (unit in amperes A), time t , (unit of measurement in hours h).

In acoustics we have an " Acoustic equivalent for ohm's law "

Relationships of acoustic sizes associated with plane progressive sound waves

Conversions of many units, similar power and energy

prefixes | length | area | book | weight | force per unit area | temperature | time | energy | power | density | velocity | acceleration | force

[top of page]

mathewsonwhispiever.blogspot.com

Source: http://www.sengpielaudio.com/calculator-ohm.htm

Share this post