Electrical Energy

Maybe you are reading this on the screen of your laptop, your mobile phone, or your tablet. Or it could be that you have printed these notes with a printer. You might be using a lamp while you are studying and you might be boiling some water with your kettle, ready for a tea break.

All of these machines have something in common: they use electrical energy to work. In our day-to-day, electrical energy is present in almost everything we do, from waking up in the morning with an alarm to the film we see at night just before going to sleep. But, what is electrical energy?

When a potential difference is present across two points in an electric circuit, charges in the circuit will experience an electric force. Under the influence of this force, charges accelerate and so gain kinetic energy. Therefore, we can understand electrical energy as a form of kinetic energy that is gained by electric charges when they experience an electric force.

Electrical energy formula

We say that the kinetic energy gained by a charge under the influence of an electric force is equal to the electrical work done by the force. This amount of electrical work can be calculated with the following formula:

$E=Pt$

Or in words

$\mathrm{Energy}\mathrm{transferred}=\mathrm{power}\times \mathrm{time}$

where,

• $P$is the power. The standard unit is the watt ($\mathrm{W}$)

• $t$ is the time during which the energy is transmitted. The standard unit is the second ($\mathrm{s}$).

• $E$is the energy transferred, equal to the electrical work done. The standard unit for energy is the joule ($J$).

The potential difference is related to the amount of electrical work that is needed to move a charge in an electric field between two points. This relation allows us to express the amount of electrical work transferred using the following expression:

$E=QV$

Or in words

$\mathrm{Energy}\mathrm{transferred}=\mathrm{charge}\times \mathrm{potential}\mathrm{difference}$

where,

• $Q$is the charge flow. The standard unit is the coulombs ($\mathrm{C}$).
• $V$is the potential difference we have already defined. The standard unit is the volt ($\mathrm{V}$).
• $E$is the energy transferred. The standard unit for energy is the joule ($J$).

Thanks to the potential difference provided by batteries in electrical circuits, charges move from one point to another through the circuit - this is why we say we need a potential difference to generate electrical energy.

Now we have a clear concept of what electrical energy is. But, how does this movement of negatively charged particles affect us? Earlier we have seen some situations where electrical energy is used but now we are going to see more situations where electrical energy is important.

Electrical energy examples

• Light: Some devices convert electrical energy into light energy or other forms of electromagnetic radiation. Electrical energy can be transformed into light in different ways. One way to obtain light with electrical energy is by passing electricity through certain materials that heat up and emit light if they reach high enough temperatures. That is what happens with incandescent bulbs. LEDs are also powered electrically, but they are more efficient that incandescent bulbs because they do not produce additional wasted heat energy.

  Devices that transform electrical energy into light are:

  • Bulbs, famously associated with the inventor Thomas Edison (although the claim that he invented it is disputed amongst historians of science).
  • LED lights
  • Torches
  • Light bulbs are one of the many devises that transform electrical energy into light.

• Thermal energy: Electrical energy can also be transformed into thermal energy or heat. As mentioned before, when the electric particles move through some materials they provoke an increase in their temperature. This allows some devices to heat. It is important to see that not all the materials increase their temperature in the same way, some do it much faster than others. That depends on their specific heat capacity.

  Some devices that use electrical energy to transform it into heat are:

  • Toaster
  • Electric radiator
  • Kettle

• There are lots of other examples where electrical energy is used. For instance, we use electricity in our bodies: In your brain, there are cells called neurons that allow you to think. To perform their function, they transmit information between themselves thanks to small electric pulses. Also, your muscles respond to small electrical currents. Or even in nature, lightning is a visible transmission of electrical charges from one point to another, therefore they are an example of a naturally occurring phenomenon in which electrical energy is transferred from one place to another.

Transmission of electrical energy

Electrical energy is generated far from cities and villages, as we do not want those areas to be plagued by noise pollution, and sometimes it is more productive to place generators in specific areas; for example solar panels are better placed where they are not obscured by buildings/structures, and some places are windier than others, meaning careful choices about where to place wind turbines can be made in order to maximise their efficiency in producing electricity.

This is the reason why the transmission of electrical energy from where it is generated to populated areas is so important. Generally, electrical energy can be transported easily and without a huge cost.

The main method to transport electrical energy over long distances is using power lines. These lines allow us to transport electricity in an efficient but cheap way. The transmission of electrical energy with power lines can be divided into two steps: primary and secondary transmission.

1. Primary transmission: When leaving the generators, the electrical energy will have a voltage between$11\mathrm{kV}-33\mathrm{kV}$, approximately. Transporting the electricity in an efficient way with this voltage range would be difficult and expensive. Therefore, the voltage is increased to a range that is between$100\mathrm{kV}-700\mathrm{kV}$, or higher, using a transformer. These values depend on the country, the system used and the distance because the longer the electricity has to travel, the higher the voltage will need to be. By increasing the voltage, the electric current is decreased because the electrical power is maintained as constant. This will reduce the losses and the electrical energy will be transported more efficiently, because high currents lead to energy losses in the form of heat energy.
2. Secondary transmission: Then the electricity travels via overland or underground power lines, using normally the first one for long distances. This electrical energy arrives at a receiving station, the voltage is stepped down to$33\mathrm{kV}-66\mathrm{kV}$and it is again sent to another substation. When it arrives at the substation this voltage is reduced once more to$11\mathrm{kV}$and is distributed through the local area using its wiring system.
3. Finally, the electrical energy is distributed in the city or village using the wiring system mentioned. The voltage will be adjusted again to values under$1000\mathrm{V}$before arriving to the houses and offices where it will be used.

Transmission towers are used to transport energy.

Advantages of electrical energy

As we have seen, we are surrounded by electrical energy in our day-to-day. What are the advantages of this electrical energy?

It is important to clarify that advantages is a general term and we could consider a range of advantages of using electrical energy. Here we are going to list some really important ones:

• Electric energy can be stored. We use some devices such as batteries or accumulators. This is why we can use our smartphones and tablets far from home, without the need for plugging them in every second.

• As we have seen, it can be transported easily. Transporting electricity turns out to be easy and not super expensive. To transport it, the voltage is adjusted in the electric station to minimize the energetic loss and then it is transported from one point to another using an underground system of wires.

• It is a broadly useful type of energy. As we have seen, we can convert electrical energy into other types of energy using domestic appliances or various electrical devices.

• There are clean ways to generate it. Generating electricity is one of the main problems, as it can not be found in nature. One of the ways we can generate electricity is from renewable sources.

  Some examples of renewable energy sources:

  • Solar energy generates energy from the sunlight with solar panels
  • Wind energy generates energy from the wind with turbines
  • Hydropower generates energy from the movement of water
  • Energy from solid biofuels

  You can find more information about renewable energy here on StudySmarter.

Disadvantages of electric energy

Electrical energy has transformed society, but there are some drawbacks to electricity. Here are some disadvantages worth mentioning:

• The main disadvantage is that most electrical energy produced today is non-renewable. Renewable energy is energy that is produced such that it will replenish at least the rate that we use it.

  Examples of non-renewable energy are:

  • Fossil fuels like coal, oil and gas
  • Nuclear energy that uses uranium (although nuclear energy's inclusion is heavily debated)

• High currents are harmful to humans. This means that electricity can be dangerous and is why there is no shortage of health and safety precautions put in place to protect us from its potentially harmful effects.

Importance of electrical energy

Electricity is present in almost every aspect of our day-to-day lives and we use it in almost everything we do. Some of the countries that use more electrical energy than most are the United States, Canada, Norway, Sweden, and Australia.

That is why we need clean ways to obtain it and try to minimize costs when generating it and transporting it.