# Watt

**What is a watt?**

Watt is the international standard power unit. Usually the watt is associated with the unit of electric power, that is, linked to electricity. However, this unit of the international measurement system is also used to refer to mechanical energy.

James Watt (1736-1819), the inventor of the steam engine, accepted it as the power unit in the SI unit system. It is the unit that measures the energy conversion rate (joules) divided by seconds. The watt symbol is represented by the letter W.

1W = 1 J/s

In mechanics the watt is the power developed by a force of a Newton applied to a point that moves one meter for a second. That is, if the point on which a force of a newton is applied moves at a speed of 1 m / s, the power is equal to 1 watt:

1W = 1N·1m / 1s

In electromagnetism, a difference in electrical potential in volts (V) occurs when an amperage current flow (A) is a watt, that is:

W = VA

## What is a megawatt?

In the nuclear energy sector it is common to talk about megawatts to refer to the power of a nuclear plant.

The megawatt is a unit of power equivalent to one million watts. Many applications can be found in which the transfer, generation or consumption of energy is on this scale, some of the possibilities can be found even in nature, such as the electric shock of lightning, or the dissipation of energy in large waterfalls are in figures of the order of the megawatt, an example would be the energy dissipated in the Dettifoss waterfall in Iceland (class 7 according to the classifications of waterfalls by volume) where the variation of the average potential energy of the waterfall is of this order.

Examples of machinery that works with powers of this order are for example large electric motors, large ships (such as aircraft carriers and submarines), special machinery and some research and search equipment such as large lasers or supercolisionadors. A large residential or commercial building can consume some megawatts of electrical power and energy for heating.

The productive capacity of electric generators operated by public services can also be measured in MW. In the railway world, modern high-power electric trains can have a maximum power of 5 or 6 MW, although many machines produce much more, the Eurostar, for example, consumes more than 12 MW - while heavy diesel-electric locomotives may typically require 3 to 5 MW. In the field of nuclear energy, some plants may have net capacities between 500 and 1300 MW.

The oldest citation of the term "megawatt" appeared, according to the Oxford English Dictionary, the Webster's International Dictionary of English Language. The OED also notes that the term megawatt appeared on November 28, 1947 in an article in the journal Science (506: 2).

## Electric megawatt

The electric megawatt (represented by MWe) is the electrical output of a power plant in megawatts, in our case, in a nuclear power plant. The electrical power of a nuclear power plant is equal to the thermal power generated by nuclear fission reactions in the nuclear reactor core multiplied by the efficiency of the power plant. That is, the electric megawatt is the electric power generated, while the megawatt is the thermal power generated by the nuclear reactor before being converted into electricity.

The efficiency of the power plants of the light water nuclear reactors is 33 to 35% compared to up to 40% for modern fossil fuels of coal, oil or gas.

## Power examples

If a person removes a mass of 100 kilos from a 3-meter ladder in 5 seconds, his work is approximately 3,000 (j = Nm).

(Note: g: the gravitational acceleration is approximately 9.8m / s ^{2} , so the body weight is 100 kg x 9.8 m / s ^{2} = 1,000 N. Y, work (joules) = force (Newton) x It is the trajectory (meter).

The power deals with how quickly this is done. So, if the power is higher, the same work is done more quickly.

Power = work / time. In our example, 3,000 Nm of work is done in 5 seconds Power (watts) = 3000/5 (Nm / s) = 600 watts available.

A medium volume car engine is 50-100 kW (kilowatts). At medium speed, it produces half the power. Larger or higher performance vehicles have more powerful engines.

A normal household bulb has a power of between 25 and 100 watts. Fluorescent lamps typically consume 5 to 30 watts to produce a similar amount of light, while similar LED lamps use between approximately 0.5 and 6 watts of power.

A normal hydropower plant produces 200-300 MW (megawatts).

Last review: October 29, 2018