International standard units of measurement are generally lowercase. Only units named after scientists, such as volts ( V ), amperes (A ), kelvins (K) , and watts (W) , are capitalized to show respect for the scientists who created them. Other units not named after individuals are generally lowercase. This explains why W is capitalized.
Secondly, for quantifiers, the initial order of magnitude is generally lowercase. If the letters are the same, uppercase and lowercase often distinguish different orders of magnitude. For example, in m Ω and MPa , lowercase m represents 1 × 10⁻³ , while uppercase M represents 1 × 10⁶ . Therefore, k here represents 1 × 10³ and should be lowercase. (Perhaps this lowercase k is also to distinguish it from K (Kelvin).
In summary, it can be observed that kW should have k as lowercase and W as uppercase.
Regarding this question, even if you use all capital letters, people can still understand it. The main point is that from an academic perspective, we should write according to the national standards.
The standard symbols for units of measurement must be correct.
The capitalization of letters is not arbitrary. For example, A , V , W , kV , kW , kVA , kvar , lx , km , etc., must all use legal units of measurement. Special attention should be paid to the correct capitalization of unit symbols. Unit symbols derived from personal names, such as A , V , W , N , Pa , and prefixes for megawatts (M) and above, such as M and G, should be capitalized; otherwise, they should be lowercase, such as kV , MW , kvar , km , etc. For information on units of measurement, please refer to Chapter 16 , pages 773-783 of the "Industrial and Civil Power Distribution Design Manual" .
On November 16 , 2018 , the 26th General Conference on Weights and Measures adopted a resolution to "revise the International System of Units," officially updating the definitions of four base units , including the international standard unit of mass, the kilogram . The new International System of Units redefines the kilogram (mass), ampere (electric current), kelvin (temperature), and mole (amount of substance) using physical constants.
Basic nouns
Voltage
Voltage, also known as potential difference, is a physical quantity that measures the energy difference per unit charge in an electrostatic field due to differences in electric potential. This concept is similar to the "water pressure" caused by differences in water level . Voltage is the cause of the directed movement of electric charges, forming an electric current. The reason current can flow in a conductor is because of the difference between high and low electric potentials within the current. This difference is called potential difference, or voltage. In other words, in a circuit, the potential difference between any two points is called the voltage between those two points.
Voltage is usually represented by the letter U. The unit is the volt ( V ), abbreviated as V, and represented by the symbol V : 1kV = 1000V ;
Note: Voltage unit is kV ( k is lowercase, V is uppercase).
Current
The amount of charge passing through a cross-section per unit time is called current. Because of the existence of voltage (potential difference), an electric field is generated, which causes the charges in the circuit to move in a specific direction under the action of the electric field force, thus forming the current in the circuit.
It is usually represented by the letter I, and the unit is A (ampere) . There are A (ampere) , kA (kiloampere) , and mA (milliampere) ; 1kA=1000A, 1A=1000mA .
Note: In the units kA and mA , k and m are lowercase, and A is uppercase.
Battery
In physics, electric charge represents the amount of electrical charge carried by an object. Here, we refer to the amount of electrical energy used by electrical equipment or users, also known as electrical energy or electrical work, which is the cumulative value of power over a certain period of time.
Units: kilowatt-hour (kW · h) , megawatt-hour (MW · h ).
Note: Units are kWh ( k lowercase, W uppercase, h lowercase) and MWh ( M uppercase, W uppercase, h lowercase).
power
Power refers to the work done by an object per unit time; in other words, power is a physical quantity that describes how quickly work is done. For a given amount of work, the shorter the time, the greater the power.
The formula for calculating power is: Power = Work / Time.
Note: Units are W (uppercase English letter W ), kW (k is lowercase, W is uppercase ) , MW (all uppercase letters), 1MW=1000kW , 1kW=1000W .
Active power
Active power refers to the electrical power required to maintain the normal operation of electrical equipment, that is, the electrical power that converts electrical energy into other forms of energy (mechanical energy, light energy, heat energy); or the power consumed by the purely resistive part of a circuit, and its unit is W. ( For example: a 5.5 kW motor converts 5.5 kW of electrical energy into mechanical energy to drive a water pump to pump water or a threshing machine to thresh grains; various lighting equipment converts electrical energy into light energy to provide illumination for people's lives and work.)
The symbol for active power is P, and the units are watts ( W ), kilowatts ( kW ), and megawatts ( MW ).
Note: Units are W ( uppercase ) , kW (k lowercase, W uppercase ) , MW ( M and W are both uppercase).
Scientists who named physical units after themselves
▲ Alessandro Volta
Alessandro Volta, a renowned Italian physicist, is famous for inventing the voltaic pile in 1800. He died on March 5 , 1827 , at the age of eighty-two. In his honor, the unit of electromotive force was named the volt ( V ).
▲André Marie Ampère
André -Marie Ampère was a renowned French physicist, chemist, and mathematician. His groundbreaking research on electromagnetism between 1820 and 1827 earned him the title "the Newton of electricity." In his honor, the international unit of electric current ( A ) is named after him.
▲Kelvin
Kelvin, whose real name was William Thomson, was a renowned British physicist. He was awarded the title of Lord Kelvin by Queen Elizabeth II for his scientific achievements and contributions to the construction of the Atlantic Cable, hence the posthumous name Kelvin. He established the absolute temperature scale, redefining the melting point of water to 273.7 degrees Celsius and the boiling point to 373.7 degrees Celsius. In honor of his contributions, the unit of absolute temperature is named after the Kelvin (K) .
▲James Watt
James Watt, a British inventor, was a key figure in the First Industrial Revolution. In 1776 , he created the first practically usable steam engine. After a series of significant improvements, it became a "universal prime mover," widely used in industry. He ushered in a new era of energy utilization, leading humanity into the "Steam Age." To commemorate this great inventor, the unit of power was designated the "watt" (symbol W ).
