Why is the voltage kV lowercase k

Q: "Why is K lowercase for voltage kV?

International standard units of measurement are usually in lower case. It is used only in cases involving units named after names, such as volt V, ampere A, Kelvin K, Watt W, etc., In order to show respect for the scientist's predecessors, the upper case is used, and the rest of the units not named after people are generally lowercase. This explains why V is uppercase.

Second, for quantifiers, the initial magnitude is generally lower case. For example, mω and Mω are different orders of magnitude in case of the same letter. Lowercase m means 1 x 10^-3. Capital M means 1 times 10 to the sixth. So k here means 1 times 10^3, in lower case. (Maybe this lowercase k is just to distinguish it from K Kelvin.) So, kV should be k lowercase and V uppercase.

In fact, even if all caps, people can understand. From the academic point of view, the national standard is how to use, we have to write in accordance with the standard.

Bring about V​

Alessandro VOLTA, Italian PHYSICIST, FAMOUS FOR HIS INVENTION OF THE VOLTAIC REACTOR IN 1800, DIED ON March 5, 1827 AT THE AGE OF 82. The unit of electromotive force was named the volt in his honor.

Bring about ampere a.

Andre Marie Ampere was a famous French physicist, chemist and mathematician. Ampere in 1820 ~ 1827 on the effect of electromagnetic research outstanding achievement, known as the "Newton of electricity" in memory of him, the international unit of electric current is named after his surname.

Bring about W​

James Watt, a British inventor, was an important figure in the first Industrial Revolution. The first practical steam engine was built in 1776. After a series of major improvements, it became a "universal prime mover" and was widely used in industry. He opened up a new era of human use of energy, so that mankind went into the "steam age". Later generations, in order to commemorate this great inventor, the unit of power as "watt" (" watt ", symbol W).

19bcbf86fd3e9ee0d243e84cce3ffa13Electric power base noun

"The voltage

Voltage, also known as potential difference or potential difference, is a physical quantity that measures the energy difference of a unit charge in an electrostatic field due to different levels of electric potential. This concept is similar to the "water pressure" caused by high and low water levels. Voltage is what drives the charge to move in the right direction, creating a current. Current flows through a wire because of the difference between a high potential and a low potential in the current. This difference is called the potential difference, also known as voltage.

In other words, the potential difference between any two points in a circuit is called the voltage at those points. The letter U is usually used for voltage. The unit is volt (V), or volt for short, denoted by the symbol V 1kV=1000V;

​note: Voltage unit: kV (K in lowercase, V in uppercase)

"The current

The amount of charge passing through the cross section per unit time is called current. Because of the existence of voltage (potential difference), the electric field strength is generated, so that the electric charge in the circuit is affected by the electric field force and produces directional movement, thus forming the current in the circuit.

Usually denoted by the letter I, the unit is A (ampere), there is A (ampere),kA (thousand ampere),mA (milliampere); 1 a = 1 ka = 1000 a, 1000 ma.

Note: In kA and mA, k and m are lowercase and A is uppercase.​


In physics, electricity is the amount of charge an object carries. Here we represent the amount of electric energy used by electrical equipment or users, also known as electric energy or electric work, which is the cumulative value of power at a certain time.

Unit: kW·h, MW·h.

Note: Units kWh (K lowercase, W uppercase, H lowercase), MWh (M uppercase, W uppercase, H lowercase)

"The direct current (dc)

Direct Current (DC) refers to the direction and time of the current does not change periodically, but the magnitude of the current may not be fixed, and produces a waveform. Also known as constant current. General dry battery, the current in the battery is direct current.

The alternating current (ac)

​An Alternating current is a current whose magnitude and direction change periodically from time to time. Alternating current is used mostly in the generation, transformation, distribution and marketing of the power system.


Power refers to the work done by an object in unit time, that is, power is a physical quantity describing the speed of work done. The amount of work is fixed, and the shorter the time, the greater the power value. The formula for power is power = work/time.

Unit: W (capital letter W)

KW (K in lowercase, W in uppercase)

MW (all capital letters)


1 kw = 1000 w.

"Active power

It refers to the electrical power needed to maintain the normal operation of electrical equipment, that is, to convert electrical energy into other forms of energy (mechanical energy, light energy, heat energy); ​or the power consumed by the purely resistive part of the circuit, in W. (such as: 5.5 kW motor is to convert 5.5 kW of electric energy into mechanical energy, drive the pump pumping or threshing machine threshing; ​various lighting devices convert electrical energy into light energy for people to live and work. The sign of active power is denoted by P.

Unit: Watt (W), Kilowatt (kW), megawatt (MW).

Note: Units W(uppercase), kW(lowercase K, uppercase W), MW (both uppercase M and W)

"Reactive power

When alternating current passes through pure resistance, electric energy is converted into heat energy and active power is consumed. However, when alternating current passes through pure capacitive or inductive load, no work is done and the power consumed is reactive power.

Reactive power is the electrical power used to exchange electric and magnetic fields in a circuit and to establish and maintain magnetic fields in electrical equipment. It does not do work, but is transformed into other forms of energy.

All electrical equipment with electromagnetic coils, to establish a magnetic field, it is necessary to consume reactive power. (For example: 40 watts of fluorescent lamp, in addition to more than 40 watts of active power (ballast also needs to consume part of the active power) to light, but also need about 80 watts of reactive power for the ballast coil to establish alternating magnetic field with.

Because it does no work, it is called "reactive work". The symbol of reactive power is denoted by Q, and the unit is var or Kvar.)

Reactive power is not useless power, it is very useful. The magnetic field of the rotor of the motor is established by obtaining useless power from the power source.

The transformer also needs reactive power to make the primary coil of the transformer produce a magnetic field and induce a voltage in the secondary coil. Therefore, without reactive power, the motor will not rotate, the transformer can not change the voltage, the AC contactor will not pull.

In order to illustrate the problem vividly, here is an example: rural water conservancy needs to dig earth transport soil, soil transport with a bamboo basket filled with soil, the soil picked off is like active power, pick empty bamboo basket is like reactive power, bamboo basket is not useless, how can the soil be transported to the embankment?

Note: Unit var (V, A, R are all lowercase), KVAR (K lowercase, V lowercase, A lowercase, R lowercase).

"Apparent power

In power networks, the product of voltage and current is called apparent power, denoted by S, that is, S= UI. When the load in the network is all pure resistance, the apparent power is equal to the active power, usually due to the presence of inductive or capacitive load in the grid, so the apparent power is greater than the active power.

To show the difference, the apparent power is not measured in watts (W), but in volt ampere (VA) or kilovolt ampere (kVA). In power systems, apparent power reflects the capacity of equipment. The product of rated voltage and rated current of electrical equipment is the capacity of the equipment.

Note: VA(V,A are all uppercase), kVA (K lowercase, V, A uppercase).

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