Just think about turning on a light switch and the entire room is filled with light. That is how electrical energy can work its magic. It is that which provides the impetus for many activities in our everyday existence. But what exactly is it?
Electrical energy is not only the ability to light up a bulb or provide power to a machine. It’s a versatile tool capable of causing various effects.
Thermal: It can produce light, heat, electricity such as in a toaster or an oven.
Electromagnetic: It can create magnetism which is crucial in the manufacturing of motors and transformers.
Mechanical: It can rotate turbines and other motors and make them work in order to accomplish their intended function.
Electrical: It can even power other electrical devices which in turn create a domino effect of useful actions.
Electrical Energy can be Stored
The electrical energy we use in our homes and industries is not created out of thin air. We produce it through different processes such as batteries, generator that employs mechanical energy to produce electricity or solar panels that harness energy from the sun.
However, there are occasions when we require this energy immediately accessible. That is why storage is so important. Electrical energy can be stored in batteries, capacitors or even create a magnetic field to store it by using fuel cells. This helps us store the energy for use at a later time when it is required.
The Law of Conservation: Energy Transition not Generation
Do you recall the Law of Conservation of Energy which you learned in your science classes? This postulates that energy cannot be created or destroyed but can be transferred from one form to another. Even electrical energy does not deviate from this law. Energy cannot be created from the scratch, but it can be transformed from one form to another and the same applies to this energy.
Electrical Machines and Energy flow
Electrical machines are like energy chameleons since they are capable of transforming energy from one form to another. They are particularly good at converting one form of energy into another, which makes them useful in a variety of contexts.
For instance, let us consider a lamp that is as simple as one can imagine. It transforms electrical energy into the light that enlightens our rooms and in the process, produces some thermal energy. This is the major advantage of electrical energy – it is very easy to convert into many other types of energy!
Work and Energy: The Two Faces of the Same Coin
However, there is a small catch to electrical energy, it needs a slight encouragement to do its job. This force is due to ‘work’ done to shift electrons. These tiny particles require that they move through a conductor such as a wire in order to form a current. This energy is stored in the flow in the form of energy by the work done to move these electrons.
Well, what do we mean by work? It is in fact the mechanism through which energy is transmitted or changed from one form to another. I like to define it as the work done to get a particular outcome. Energy is the capacity to do work and therefore, it is like a two sided coin.
It is applicable to electrical systems as well as mechanical and thermal systems of the building. However, these forms of energy can be converted – a motor turns electrical energy into mechanical work while a power plant turns heat energy into electricity.
Therefore, electrical machines are the transformers par excellence, utilizing the work-energy principle to light up the world with a never-ending stream of energy!
Understanding Voltage: The Force Behind Electrical Current
From the previous discussion, we’ve learned that energy is the capacity to do work and it is expressed in Joules. Now let me ask you, where do you see this in the context of electricity? This is where voltage (V) is used – it is the driving force or the force that helps in moving the electrons in a circuit.
Imagine a river. Water can flow through pipes only if there is a pressure pushing it through the pipe. Similarly, electrons require voltage to push them through a circuit from point A to point B. This force, or voltage difference, is like the slope of a river and this force is the voltage difference. This is because as the incline becomes steeper, which is equivalent to the voltage, the water flows at a faster rate, in this case, the electrons.
One Volt: The relationship between Work and Charge
The technical definition of a volt is quite specific: It is the amount of work done or energy spent to transfer charge of one Coulomb between two points in the circuit. In layman terms, one volt is the amount of pressure that is needed to push one Coulomb of electrons from one terminal to another.
Voltage as a Formula: The study and practice of both economics and public policy require an understanding of how the various components fit together.
We can express this relationship mathematically using the following formula:
1 Volt = 1 Joule per Coulomb, or 1Volt = 1Joule / 1Coulomb).
This equation means that volts (V) are equal to the energy (joules) divided by the charge (coulombs). In other words, voltage is defined as the amount of work done per unit charge placed in motion.
As the voltage increases, there is more ‘pressure’ on the electrons and therefore they move with greater force or current. This concept is central to comprehending the operation of electric circuits and voltage control of electrons in the circuits.
Solving an Electrical energy Problem
How much voltage is there at the battery’s terminal when 12 coulombs of charge is moved through an electrical circuit using 130 joules of energy???
Solution:
From the information given (130 joules and 12 coulombs), we cannot directly establish the terminal voltage of the battery. Heres why:
We are surely missing a crucial piece of information, resistance.
The amount of voltage required to transport a given number of coulombs through a given circuit depends on the resistance offered to the charge.
Essentially, work done per unit charge moved is the definition of potential difference (voltage).
We know the amount of work done (130 joules) and the charge transferred (12 coulombs).
voltage = J/C
The potential difference = 130 J / 12 C = 10. 83 volts
Important Note:
This calculated potential difference gives the voltage of the battery as it would be in the ideal condition without any resistance within the battery.
However in real situations, batteries are not perfectly ideal.. they have some internal resistance and therefore the terminal voltage will be slightly less than the calculated potential difference.
Amperes (A) in Electrical Current: An Introduction
We have already discussed the theory of electrical charge, expressed as Coulombs (C). Circuits are powered by the current produced by this charge flow. But to add to the confusion, the letter “C” can also stand for capacitance.
In order to avoid this, the usual symbol for electrical charge is either a capital “Q” or a lowercase “q,” which represent the “quantity” of charge. To put it another way, Q = 1C or 1 coulomb.
The “quantity” (Q) of charge can be either positive (+Q) or negative (-Q), which is a crucial point to remember. This is an indication of an imbalance in the material: too many electrons, which are carriers of negative charges, or a lack of electrons, which are not behaving as positive charges.
We are aware that an electric current is the movement of an electrical charge along a closed circuit, often in the form of electrons. What causes these electrons to travel, though?
Voltage: The Force that Drives the Flow
This is when our old friend voltage (do you remember it from before?), comes into action. Voltage, which is defined as the potential difference between two places, supplies the electrical energy required to move the charge, or electrons, through the circuit and produce current.
No Push, No Flow
Imagine it like a stream of water going downward. The water (or electrons) will not flow if there is no potential difference (difference in height). Because of this, there cannot be a voltage differential between two sites, nor can there be any charge movement or current. This explains why static electricity doesn’t produce a current when charge accumulates but doesn’t flow.
Measuring Current: Rate of Flow
What quantity of charge constitutes a current if current is the rate at which charge moves? By determining the quantity of charge (electron) that passes through a certain location in the circuit in a second, we may determine the magnitude of an electric current in amperes (A).
This means that one coulomb of charge flowing across a point in a unit second of time equals one ampere of current. The more charge flowing past this point in a unit of time, the larger the current.
So, one coulomb of charge per second is equivalent to one ampere (A) of electrical current.
Therefore, 1A = 1C/s
Unit of Electric Current: Ampere
1Ampere = 1Coulomb / 1Second = Q / t
The above formula, the symbol Q as representing the charge in coulombs and the symbol t as the time in seconds that this charge moves. This is the reason when we speak of electrical current we are speaking of not only the amount of charge but also, the direction of flow of the charge.
Depending on the context, when writing about electrical current, we use the letter ‘I’, uppercase ‘I’ for constant DC current, and lowercase ‘i’ for changing AC current. It is for this reason that the lowercase ‘i’ always tells us exactly what the current is at a specific time (i(t)).
To assist in remembering the arrangement of these things, one can picture a triangle that interconnects Q, I, and t to indicate where they are located in the formula for current.
The Ampere Triangle
By rearranging the original formula, we can obtain different versions that express identical relationships between the variables Q, I and t.
Solving an Electrical Energy Problem
Problem#1: We have a circuit with 700 coulombs of electrical charge passing through a certain point in 2 minutes. Our goal is to calculate the total current passing in the circuit.
Solution:
This problem can be solved by using current (I), which is the rate of flow of electric charge (Q) through a particular area in a certain time (t). undefined
I = Q / t
where:
I: Current (in amperes, A):
Q: Charge (in coulombs, C)
t: Time (in seconds, s)
Step 1: Convert Time into Seconds
Since the time is given in minutes, it is converted to seconds so that the unit of current, amperes, could be used. They include 60 seconds in a minute and 60 minutes in an hour. Therefore:
Time (t) = 2 minutes * 60 seconds/minute = 120 seconds
Step 2: In the next step, you have to apply the formula that you have derived in the previous step.
Charge (Q) = 700 coulombs
Time (t) = 120 sec
I = 700 C / 120 s = 5. 83 amperes (A)
Answer:
Hence, the current that passes through the circuit is about 5. 83 amperes.
Problem#2:
Suppose we have a circuit with a resistor. If a constant current of 2 amperes (A) flow through this resistor for 100 seconds, how much electrical charge (in coulombs, C) will pass through the resistor??
Solution:
We ae able to solve this problem using the principle of current (I) which is the rate of flow of electric charge (Q) over time (t). This relationship is expressed by the formula:
Q = I * t
where:
- Q: Charge (in coulombs, C)
- I: Current (in amperes, A)
- t: Time (in seconds, s)
We have the following Values:
- Current (I) = 2 amperes (A)
- Time (t) = 100 seconds (s)
Finding the Charge Flow (Q):
Simply just apply the formula and substitute in the given values:
Q = 2 A * 100 s = 200 coulombs (C)
Answer:
So we have, 200 coulombs of electrical charge that will flow through the resistor in 100 seconds.
Understanding Electrical Power: Watts and Work
So far we know that electrical circuits rely on two fundamental concepts: V and I are the two fundamental parameters in the electrical circuit, abbreviated as voltage and current respectively.
However, how do these two factors relate to each other to illustrate the practical use of electrical energy? That is where the idea of electrical power (P) comes from.
Power: The Rate of Work Done
The term electrical power means the rate at which electrical work is done or, in other words, the rate at which energy is used up.
Earlier, we looked at voltage as the work done per unit charge moved (Joules per Coulomb). On the other hand, current is the rate of charge flow or the amount of charge in Coulombs moved per second.
We may define electrical power (P) by taking into account the sum of these two quantities: voltage (V): defined as Joules per Coulomb (V = J/C), and current (I): defined as Coulombs per second (A = Q/t). This is because, according to the formula P = VI, electrical power may also be expressed as the product of voltage and current.
Understanding Watt
V = J / C and I = Q / t
Since Q = 1C
If, P = V * I = (J / C) * (Q / t)
Then, P = (J / C) * (C / t) = J / t
This relationship between voltage and current helps us to perceive electrical power in a different way. It also shows the rate at which energy is used or work is completed per second. Put another way, one joule (J) of energy is transferred in one second (s) by one watt (W), the unit of electrical power.
This indicates that watts (W) and joules per second (J/s), two units of measurement for electrical power, are both possible.
With assurance, we may declare the equivalent status: 1 watt is equal to 1 joule per second (1 W = 1 J/s).
Understanding Power
1 watt (W) = 1 joule/second (J/s)
It is important to understand the connection between watts and joules per second. We are aware that one joule per second (J/s) equals one watt (W).
This suggests that one watt acting for a certain amount of time can be used as an alternate expression for one joule (J) of energy.
Using this reasoning we may combine power (rate of energy consumption) and time to calculate total electrical energy consumption. E = VIt is the formula for electrical energy (work done) where V is voltage in volts (V), I is current in amperes (A), and t is the time in seconds (s). E stands for energy in joules (J).
To find the total energy used, we just have to multiply the power (VI) by the time (t) using this formula.
It is crucial to remember that electrical energy units are determined by the units of power and time. For example, if we measure power in kilowatts (kW) and time in hours (h), the electrical energy spent is calculated in kilowatt-hours (kWh). So that means, 1 kWh indicates the amount of energy utilized when 1 kW of electricity is consumed for one hour.
Solving a Problem for Watts
Let’s imagine that a 200 Watt light bulb is powered on for 1 hour and then switched OFF. How do we calculate how many joules of electrical energy was consumed by the lamp for that period of time?
Solution:
Step 1: Convert Time to Seconds
Electrical power is typically measured in watts (W), and energy consumption is measured in joules (J). However, the time in the problem is given in hours (h), therefore we have to convert hours to seconds for our calculations, this is because the formula for energy uses seconds.
There are 3600 seconds in 1 hour. So, we can convert the time as follows:
t (seconds) = t (hours) * 3600 seconds/hour
t (seconds) = 1 hour * 3600 seconds/hour = 3600 seconds
Step 2: Calculate Electrical Energy Consumed
We can use the formula for electrical energy consumption:
Energy (E) = Power (P) * Time (t)
E (Joules) = P (Watts) * t (seconds)
Step 3: Solving for Energy Consumption
E (Joules) = 200 Watts * 3600 seconds
E (Joules) = 720,000 Joules
Therefore, the 200 Watt light bulb used 720,000 Joules of electrical energy during its 1 hour illumination.
Although joules are the scientific unit of electrical energy, kilojoules (kJ) are more commonly used in everyday scenarios. This is simply because one joule is just a tiny quantity of energy. Kilojoules (kJ = 1,000 J) are a more practical measurement unit for solving calculations.
Besides kilojoules, there are even bigger units for measuring electrical energy:
Megajoules (MJ) are millions of joules (1,000,000 J).
A gigajoule (GJ) is equal to 1,000,000,000 joules.
Kilowatt-hours (kWh) are a popular unit of measurement for residential power bills. Interestingly enough, 1 kWh equals 3.6 megajoules (MJ).
The same concept is applicable to electrical power. Watts (W) represent the technical unit, although because of their tiny size, kilowatts (kW) and megawatts (MW) are more widely used. In layman’s terms, kilowatts (kW) are 1,000 watts, whereas megawatts (MW) are one million watts (MW = 1,000,000 W)..
The primary takeaway is to recognize different units:
Electrical power units are measured in kilowatts (kW) or megawatts (MW) (rate of energy consumption).
Megajoule (MJ) or kilowatt-hour (kWh) are units of electrical energy (total energy consumed).
References: About Electric Energy and Power
Electrical energy is an important concept in science