Electrical Energy
Electrical energy is defined as the kinetic energy produced as electrons move between two points. Electrical energy can therefore be the conversion of potential energy of electrons due to their movement. This movement of electrons produces electricity.
Mathematical Expressions
Electrical energy can be calculated through the product of power and time.
Electrical energy can also be calculated in terms of voltage and charge:
The expression of power is given by:
Current is defined as rate of change of charge:
Electrical Energy therefore can be expressed as:
SI Units
Electrical energy is expressed in Joules. Joules can be defined from above mathematical expression as under:
Therefore, electrical energy is one joule when a charge of one coulomb passes through a potential difference of 1 volt. Electrical energy can also be presented in watt-seconds, as from the mathematical expression below:
Commercial Units
Electrical energy is used in almost every domestic and commercial premises. Therefore, a standard commercial unit for electrical energy is used to measure its consumption. The commercial unit is called kilowatt-hour (KWH). 1kWH is also called 1 unit of energy.
Electrical Power
Power can be defined as the rate of time required to perform a particular work. Power therefore measures how much energy is being utilized to perform a certain work. For an electrical circuit, the power can be defined as the rate of delivery of electrical energy to the electrical circuit in one second time. These definitions can also be understood through mathematical representations.
Mathematical Expressions
The standard power equation is the product of voltage and current:
From mathematical expressions of electrical energy, we know:
Current is defined as rate of flow of charge:
Substituting in electrical power expression:
The above expression proves that power is the rate at which energy is being supplied to perform a certain work.
SI Units
Electrical power is measured in units of watts.
Power can also be measured from the expression below of electrical energy. The power units can therefore be derived as:
Electrical Charge
Electrical charge can be defined as the ability of an atomic particle to experience a certain force when it is placed in electric or magnetic fields. Charge is one of the fundamental components of electric current. Electrical charges are of two different types: positive charge and negative charge.
Types of Electrical Charge
Electrical charges can be either positive or negative. Positive ones mean protons which are present in nucleus of atoms and are denoted by plus ‘+’ sign. Negative ones mean electrons which orbit the nucleus and are denoted by negative ‘-‘sign.
One of the fundamental properties of an electrical charge is either it faces attraction, or it faces repulsion in presence of other electrical charges. Like charges have inherent repulsion effects on each other, while unlike charges have attraction for each other. It means that when two positive or two negatives are placed next to each other, they will experience a force to push them apart. On the other hand, if opposite charges, positive or negative charges are placed next to each other. They will experience a force to bind them close together.
Mathematical Expression
Electric current is defined as the rate of flow of charges in unit time with the below expression:
Electrical charge can therefore be expressed as:
Electrical charge, current and duration of time can be expressed in form of triangle below:
Triangle interprets that each of three parameters can be expressed in terms of others.
SI Unit
The unit of electrical charge is coulomb. One coulomb therefore be expressed as:
One coulomb represents 1 ampere of current passing through a point in 1 second.
Example 1: Electrical Charge Calculation
Calculate electrical charge if 10 ampere current passes through a point in 5 seconds.
Electrical charge is given by:
Example 2: Electrical Energy Calculation
Calculate electrical energy consumed if two 100-watt incandescent bulbs light up for 2 hours.
Electrical energy is given by:
Example 3: Electrical Power Calculation
Calculate electrical power for a 12V battery connected across 50 ohms resistors.
Electrical power is given by:
Since current (I) is unknown, using ohm’s law:
Now power can be calculated as:
Conclusion
Electrical power is defined as the rate of delivery of electrical energy in electrical circuit. Electrical energy is defined as a product of electrical power and duration of time. Electrical charge is defined as the fundamental property of an atomic particle to experience a force of pull or push in electric or magnetic fields.
