What Physics Students Need to Know About Electricity

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Are you a Physics student in Singapore wondering what are the basics you should know about electricity? If you are, then you have come to the right place. Electricity is a vast subject and supplementary practice from your school work and Physics tuition is greatly encouraged. As a start, Here are some of the important things you should know about electricity:

Coulomb’s Law

Coulomb’s law, also called Coulomb’s inverse square law, states that the electrical force between two electrically charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the distance (of separation) between them. It is expressed by the following mathematical equation:

F = (k * Q1 * Q2) / r2

Q1 is the quantity of charge in object 1 (in Coulombs), Q2 is the quantity of charge in object 2 (in Coulombs), r is the distance of separation between the two objects (in meters) and k is a constant known as Coulomb’s law constant. The value of k depends on the medium. In air, k = 9.0 x 109 Nm2/C2.

The importance of Coulomb’s law equation is that it accurately describes the electrical force between two objects whenever they act as point charges.

Current, Potential Difference and Resistance

Current: An electric current is the flow of electric charge in an electric circuit. A single electron carried a charge of 1.6 x 10-19 C. As a physical quantity, current is defined as the rate at which charge flows past a given point in an electric circuit. Mathematically, it is represented as:

I = Q / t                       where I is the current, Q is the total charge, and t is the time taken.

In SI unit, the current is measured in units of Ampere, which is the flow of electric charge past a point at the rate of 1 coulomb per second.

Potential difference: Potential difference is the difference in electric potential between two points in an electric circuit when work is done on a charge to change its potential energy. It is represented mathematically by the following equation:

V = W / Q        where V is potential difference (voltage), W is the work done and Q is charge

Or        V = E / Q         where E is energy

Since potential difference is measured in units of voltage, it is often referred to as the voltage.

Resistance: Resistance is the hindrance in the flow of electricity. More precisely, it is a measure of the difficulty in passing of an electric current from one point of a medium to another point. Mathematically, it is expressed by the following equation:

R = V / I                      where R is resistance, V is the potential difference (voltage) and I is the current.

R is measured in units of Ohm, represented by the Greek letter W.

Ohm’s Law: Ohm’s law states that the current passing through a conductor from one point to another is directly proportional to the voltage across the two points. Mathematically, it is represented by the equation I = V / R, which leads to the above equation.

D.C. Circuits

Direct current (DC) is the constant flow of electric charge from a point of high potential to another point of low potential. A D.C. circuit is an electrical circuit in which electric current flows in one direction only. Current flows in the circuit only when it is closed and stops completely when it is open. DC circuits are commonly used on low-voltage application, such as those powered by battery.

While keeping these basics in mind, merely understanding the theory is insufficient to have a good grasp of this subject. Physics is a subject of practice, get ample practice through your Physics tuition and your school work. Do not under estimate the power of completing your homework religiously!