Conas mar a Mearsáil Forcheimiceach: An Leabharlann Cuimsitheach
Cad é Fórsa Leictreach?
Fórsa leictreach is é an t-ionann ar phróduct de fórsa leictreach agus time, agus mheastar é i joules (J). Is ionann joule amháin de fórsa leictreach agus watt amháin de fórsa a chuirtear isteach ar feadh soicind amháin. Matamaiticiúl, is féidir linn scríobh:
E=P×t
áit,
E is the electrical energy in joules (J)
P is the electrical power in watts (W)
t is the time in seconds (s)
Tá fórsa leictreach agus fórsa go dlúth gaol le chéile. Is é fórsa leictreach an t-amount of electrical current that flows through a circuit due to a certain voltage difference across it. Is é fórsa leictreach freisin an ráta aonaitheach a dhéantar fórsa leictreach a sholáthar nó a chur isteach ag tréith nó córas. Is mearsaítear fórsa leictreach i watts (W), which are equivalent to joules per second (J/s). Mathematically, we can write:
P=V×I
áit,
P is the electrical power in watts (W)
V is the voltage difference in volts (V)
I is the electrical current in amperes (A)
Chun fórsa leictreach a mheastar, ní mór dúinn a bheith cinnte faoi fórsa leictreach agus an t-am a chuirtear isteach nó a chur isteach. Mar shampla, más ginearálta 100 W solas a chasadh ar feadh 10 noiméada, ansin is é an fórsa leictreach a chuirtear isteach ag é:
E=P×t=100 W×10×60 s=60,000 J
Uintí de Fórsa Leictreach
Joule is the standard unit of energy in the International System of Units (SI), but it is too small for practical purposes when dealing with large amounts of electrical energy. Therefore, other units are commonly used for measuring electrical energy, such as watt-hour (Wh), kilowatt-hour (kWh), megawatt-hour (MWh), and gigawatt-hour (GWh). These units are derived from multiplying the unit of power (watt) by the unit of time (hour).
Watt-hour (Wh) is the amount of electrical energy consumed by a device or a system that draws one watt of power for one hour. It shows how fast the power is consumed over a period of time. One watt-hour is equivalent to 3,600 joules. For example, a 15 W LED light bulb consumes 15 Wh of electrical energy in one hour.
Kilowatt-hour (kWh) is a larger unit of electrical energy that is commonly used for household appliances and utility bills. One kilowatt-hour is equal to 1,000 watt-hours or 3.6 megajoules. For example, a refrigerator that draws 300 W of power consumes 300 Wh or 0.3 kWh of electrical energy in one hour.
Megawatt-hour (MWh) is a unit of electrical energy that is typically used for measuring the output or consumption of large-scale power plants or grids. One megawatt-hour is equal to 1,000 kilowatt-hours or 3.6 gigajoules. For example, a coal-fired power plant that has a capacity of 600 MW produces 600 MWh of electrical energy in one hour.
Gigawatt-hour (GWh) is a unit of electrical energy that is used for measuring very large amounts of electricity generation or consumption over long periods of time. One gigawatt-hour is equal to 1,000 megawatt-hours or 3.6 terajoules. For example, the total electricity consumption of the United States in 2019 was about 3,800 TWh or 3.8 million GWh.
The following table summarizes the units of electrical energy and their conversions:
| Unit | Symbol | Equivalent to |
|---|---|---|
| Joule | J | 1 J |
| Watt-hour | Wh | 3,600 J |
| Kilowatt-hour | kWh | 3.6 MJ |
| Megawatt-hour | MWh | 3.6 GJ |
| Gigawatt-hour | GWh | 3.6 TJ |
Conas a Mheastar Fórsa Leictreach le Measar
Chun fórsa leictreach a mheastar, ní mór dúinn treoirlíne a bheith againn a chumas an fórsa leictreach agus an t-am a chuirtear isteach nó a chur isteach. Is é an treoirlíne sin an measar fórsa leictreach nó go simplí an measar. Is treoirlíne é an measar a mheastar an t-amount of electric energy consumed by a residence, a business, or an electrically powered device. Mheastar an fórsa iomlán a chuirtear isteach ar feadh tréimhse ama agus is é an t-uinte a úsáidtear sa chostas, an t-uinte is coitianta ná an kilowatt-hour (kWh). Úsáidtear meastair i dtithe agus i seirbhísí gnó agus i gcúrsaí AC circuits for measuring power consumption.
Tá séoraí meastair ann, ag brath ar an teicneolaíocht, an dearadh, agus an t-úsáid. Cé acu na séoraí coitianta:
Electromechanical meters: These are the traditional meters that use a rotating metal disc and an electromagnet to measure the electrical power and record it on a series of dials or a mechanical counter. They are also known as induction meters or Ferraris meters. They are simple, robust, and accurate, but they have some drawbacks, such as mechanical wear and tear, susceptibility to tampering and magnetic interference, and inability to measure reactive power or power quality.
Electronic meters: These are the modern meters that use electronic circuits and sensors to measure the electrical power and display it on a digital screen or transmit it to a remote system. They are also known as solid-state meters or digital meters. They have many advantages over electromechanical meters, such as higher accuracy, lower maintenance, remote reading and communication, multiple tariff options, and advanced features such as demand response, load profiling, and power quality analysis.
Smart meters: These are advanced meters that use digital technology and wireless communication to measure the electrical power and send it to a central system or a smart grid network. They are also known as advanced metering infrastructure (AMI) or intelligent metering systems (IMS). They have many benefits over electronic meters, such as real-time data collection and analysis, dynamic pricing and billing, outage detection and restoration, demand-side management, and customer engagement.
The basic principle of measuring electrical energy with a meter is to multiply the electrical power by the time duration for which it is applied or consumed. However, depending on the type of meter and the type of load, there are different ways of calculating the electrical power. Some of the common methods are:
Single-phase meters: These are the meters that measure the electrical power in single-phase AC circuits, which have one live wire and one neutral wire. The simplest way of calculating the electrical power in a single-phase circuit is to multiply the voltage by the current. However, if the load is not purely resistive, then there is a phase difference between the voltage and the current, which reduces the effective power delivered to the load. This effective power is called real power or active power, and it is calculated by multiplying the voltage by the current by the power factor (cosine of the phase angle). The apparent power or total power is calculated by multiplying the voltage by the current without considering the power factor. The difference between the apparent power and the real power is called reactive power or idle power, which is wasted in heating up the circuit components. The ratio of real power to apparent power is called the power factor, which indicates how efficiently the load uses electrical energy.
