Electrician common units and formulas are here, you remember a few? Come down inventory!
Electric power
It represents the current through a certain period of time in a circuit, the work done by the electric force. More energy into other forms of energy may also be said that the process of the current work process, the number of electric power generating said current conversion do much work, i.e., how much electrical power. How much size with high and low current, voltage, power duration have a relationship of current work. Applied to the higher voltage electrical appliances, the greater the current through, the longer energizing time, more current work.
W represents a power, a unit of work is: joule (J)
W=Pt
P --- Power (Unit: W w)
T --- Time (Unit: second s)
W = OFF
U --- voltage (unit: V V)
I --- Current (Unit: Security A)
T --- Time (Unit: second s)
W=I^2Rt
I --- Current (Unit: Security A)
--- R & lt resistance (unit: Europe [Omega])
T --- Time (Unit: second s)
W=U^2/R×t
U --- voltage (unit: V V)
--- R & lt resistance (unit: Europe [Omega])
T --- Time (Unit: second s)
The object of several common electrical work:
① current through the flashlight bulb, the work done per second is approximately 1J.
② current by ordinary light bulb, the work done per second is generally several tens of coke.
③ washing machine motor by a current, the work done per second is about 200J.
power
It refers to how much of the work done by the object per unit time, i.e., the speed of power is described physical work. A certain number of power, the shorter the time, the greater the power value.
P represents power, the power unit is: watt (W)
P=W/t
W --- electric power (unit: Coke j kWh or kWh)
T --- Time (Unit: second s)
P = UI
U --- voltage (unit: V V)
I --- Current (Unit: Security A)
P = U ^ 2 / R (only for purely resistive circuits)
U --- voltage (unit: V V)
--- R & lt resistance (unit: Europe [Omega])
P = I ^ 2R (only for purely resistive circuits)
I --- Current (Unit: Security A)
--- R & lt resistance (unit: Europe [Omega])
Electric charge
Refers to an object or an amount of the charged particles constituting the object, the object or the Metadata is the algebraic sum of charges.
Q represents a charge, the charge unit is: Coulomb (C)
Electric current
Refer to the orientation of the mobile charge.
I denotes a current, the current is: amperes (A)
1 Amp is defined as: distance of two infinite long wire 1 meter in vacuo at equal constant current through, when the force acting on the wire per meter when 2 × 10-7 N, the conductors on the current 1 amp. Primary study 1 ampere is defined within a second amount of electric charge through a conductor cross section of 1 Coulomb, namely: 1 Amp = 1 coulomb / sec.
Some common current:
Electronic watches 1.5μA to 2μA, incandescent bulbs 200mA, phone 100mA, air conditioning 5A to 10A, high-voltage 200A, lightning 20000A to 200000A.
Current density
Current density vector physical quantity is a point and the flow direction of the current strength in the circuit described. Size equal to the unit time through a unit area of the charge, the direction vector of the normal vector corresponding cross-sectional area of the unit, is determined by a point by pointing to the positive charge of this section.
J represents the current density, current units: ampere / square meter A / m
Voltage
Also known voltage potential difference or potential difference, the energy difference is a measure of a unit charge quantity due to the difference in the electrostatic field potentials generated. Size equal to the positive charge of the unit due to the electrostatic force moving from point A to point B in the direction of the work done, the predetermined voltage is a direction from the high to low potential. The International System of Units voltage in volts (V, referred to as V), as well as units commonly used in millivolts (mV), micro-volts (microvolts), kilovolt (kV) and the like.
Voltage of the main units of the International System of Units is volts (V), referred to as V, represented by the symbol V. Is equal to 1 volt per coulomb charge 1 joule do work, i.e., 1 V = 1 J / C. Common strong voltage kilovolts (kV) as a unit, the unit may be weak voltage in millivolts (mV) microvolts (μv).
Conversion between them is:
1kV=1000V
1V=1000mV
1mV=1000μv
U represents the voltage, a voltage of the unit: volt (V)
U = IR
I --- Current (Unit: Security A)
--- R & lt resistance (unit: Europe [Omega])
U=P/I
P --- Power (Unit: W w)
I --- Current (Unit: Security A)
U = IρL / S
I --- Current (Unit: Security A)
--- resistivity [rho] (unit: ohm m Ω · m)
--- object length L (unit: m m)
--- sectional area S of the object (Unit: sq m)
resistance
It represents current conductor hindered size.
Conversion of the resistance per unit: 1KΩ = 1000Ω
R represents a unit resistor, the resistor is: ohms ([Omega])
R=U/I
U --- voltage (unit: V V)
I --- Current (Unit: Security A)
R=ρL/S
--- resistivity [rho] (unit: ohm m Ω · m)
--- object length L (unit: m m)
--- sectional area S of the object (Unit: sq m)
Conductivity
It represents a sense the current intensity conductor transmission capability.
G represents conductance unit of conductance is the object: Siemens (S) or ohms ([Omega])
G=1/R
--- R & lt resistance (unit: Europe [Omega])
G = I / U
I --- Current (Unit: Security A)
U --- voltage (unit: V V)
Resistivity
Resistivity material is used to represent the various physical resistance characteristics. The product of the ratio of the length of the original made of a substance (room temperature 20 ° C) and the cross-sectional area of the resistance of such materials is called resistivity. Independent resistivity and length of the conductor cross-sectional area and other factors, is the electrical properties of the conductor material itself, is determined by the material of the conductor, and the temperature.
ρ represents the resistivity, the resistivity units: ohm-meters (Ω · m)
p = 1 / n
--- Resistivity [kappa] (Unit: Siemens / m S / m)
ρ=RS/L
S --- cross-sectional area (unit: m square meters)
--- R & lt resistance (unit: Europe [Omega])
--- wire length L (unit: m m)
p = E / J
E --- electric field strength (unit: N / library N / C)
J --- the current density (unit: Security / m² A / m)
ρ=ρo (1+at)
--- ρo resistivity at 0 deg.] C (unit: ohm m Ω · m)
t --- Celsius temperature (unit: ° C)
A temperature coefficient of resistivity ---
Conductivity
Is used to ease the flow of charge material level parameter is described. In the formula, the conductivity is represented by the Greek letter κ. Conductivity [sigma] is the standard unit of Siemens / meter (abbreviated to make S / m), [rho] is the reciprocal of resistivity, i.e., σ = 1 / ρ
--- resistivity [rho] (unit: ohm m Ω · m)
When one amperes (A 1) of the current cross-section through the object and the presence of 1 volt (V 1) voltage, the conductance of the object 1 is S. Siemens is effectively equivalent to 1 ampere / volt. If [sigma] is the electrical conductivity (units of Siemens), I is the current (amperes), E is the voltage (in volts), then: [sigma] = the I / E
Reactance
Similar to the DC circuit current to the resistor impediment, in an AC circuit, the capacitance and inductance will impede current, called reactor, which is also called an ohmic measuring unit. With the reactance circuit AC frequency varies, and causes a phase variation circuit current and voltage.
X represents reactance, reactance units: ohm (Ω)
X=XLXc
Circuit reactance XL ---
Circuit reactance XC ---
Inductive reactance
Because there is generally an inductive circuit (e.g. coils) circuit resulting electromagnetic field changes, produces a corresponding electric power flow of electrical current. The larger the change in current, i.e., the larger the circuit frequency, the greater the inductance; inductance will cause a phase difference between the current and voltage.
XL represents reactance, in ohms (Ω).
XL=ωL
--- [omega] the angular frequency (unit: rad / rad sec / s)
--- inductance L (unit: Henry H)
XL=2πfL
f --- frequency (unit: Hz Hz)
--- inductance L (unit: Henry H)
Capacitive reactance
The higher the frequency of the alternating current, the smaller the capacitance, i.e. the capacitance smaller impediment. Phase capacitance will cause the same current and voltage across the capacitor.
Capacitive reactance is represented by Xc
Xc=1/（ωC）
--- [omega] the angular frequency (unit: rad / rad sec / s)
C --- capacitance (unit: Farah F)
Xc=1/（2πfC）
f --- frequency (unit: Hz Hz)
C --- capacitance (unit: Farah F)
Angular frequency
Angular frequency, also called the circular frequency, the value represents the phase angle in radians per unit time changes. It is the angular frequency of vibration speed of the physical description of the object, and the intrinsic property of the vibration system concerned. In the international system of units, the unit is the angular frequency in radians / second (rad / s). Each object has its own properties determined by the frequency-independent amplitude, called the natural angular frequency. Harmonic vibration system is equal to the rotation angular velocity vector of the angular frequency value.
In the harmonic vibration, 2π times the frequency of the angular frequency is called. represents an angular frequency ω, the angular frequency units: radians / second (rad / s)
omega = 2 pi = 2 pi / T
f --- frequency (unit: Hz H)
T --- Cycle
Reproduced in: https: //www.jianshu.com/p/93ea610fb19b