• Dhanush kumar S

Voltage & Current

Updated: Dec 1, 2020

Starting from our childhood, we all would have seen many appliances such as washing machines, televisions, and refrigerators in our houses. We all know that they function with the help of electric current. That electric current should be passed at appropriate voltage to those appliances otherwise they will get damaged. #Voltage and current are interdependent with each other. Natural examples of electric #current are lightning, static electric discharge.


Since this article is meant for the beginners, here we shall discuss the basic definition of voltage, current, its types, how they are related to each other, and the ways of measuring them.


Voltage


Voltage can be termed as the pressure generated by the power source of an electric circuit to move the charged electrons from one point of the circuit to another. This voltage can also be expressed in different terms such as electric pressure, electric potential difference, or electric tension. The term potential difference is nothing but the value which determines how much potential energy is required to move electrons from one point to another. A voltage may indicate the electromotive force that has been used or lost.


The derived unit of voltage is termed as volt. It is named after the Italian scientist Alessandro Volta who invented the first chemical battery. In SI units, one volt can be defined as one joule of work done used to push one coulomb of electric charge.


Circuit diagram of voltage

Voltage can be measured manually using various laws such as ohm's law, Kirchhoff's voltage law. As we know, ohm's law states that the current through a conductor is proportional to the voltage across the two points of the conductor.


Kirchhoff voltage law states that The sum of voltage or potential difference across a closed-loop is zero. Other than these two laws, measuring instruments are also used in calculating the voltage across a conductor. The instruments include a potentiometer, voltmeter, and oscilloscope. In a bridge circuit, a potentiometer compares an unknown voltage to the existing voltage to calculate. Whereas the oscilloscope amplifies the applied voltage and deflects the electron beam from its straight path. The angle of deflection is proportional to the voltage applied.


Current


Current is defined as the rate at which the electrons flow past a point or specified region. The charge carriers differ with respect to the conductor, mostly electrons but in the electrolytic conductors, the charge carriers are ions. The SI unit for measuring current is ampere. One ampere is defined as the flow of electric charges through a conductor at the rate of one coulomb per second.


Current flow

Electric currents can be manually measured by using the above-mentioned ohm's law and also by Kirchhoff's current law. The statement of current law is, the algebraic sum of currents in a network of conductors meeting at a point is zero. Devices such as galvanometers were used for measuring current before. But they measure the current flowing in circuits by breaking them at a point. Nowadays transformers are used to measure AC currents and magnetoresistive field sensors are also employed to measure high currents.


Whenever current flows through a conductor, a certain amount of heat is generated. This is known as Joule's heating effect. The amount of heat generated is directly proportional to the square of the current and the resistance of the wire through which the current is flowing.


Types of current -


If the electric charges in a system flow only in one direction then the current can be termed as Direct current(DC). The direct current though wires(conductors), semiconductors, and also in a vacuum as ions. Direct current can be generated using solar cells, thermocouples, and batteries. Alternating current can also be converted into direct current with the help of rectifiers.

Circuit diagrams having AC and DC current

If the flow of electric charges periodically reverses in a system, then the types of current can be termed as Alternating current(AC). This alternating current is provided for industrial, commercial, and even domestic purposes. Radio and audio signals are the types of alternating current. The waveform of alternating current is expressed as a sine wave.


Difference between voltage and current:

  • The electric current generates a magnetic field around them which is employed in operating motors, transformers whereas voltage generates the electrostatic field.

  • In series combinations, the amount of current flowing through all the elements is the same and the voltage is the sum of the voltage drop across each component.

  • In parallel combinations, the current flowing through each resistor can be found using ohm's law. Voltage is the same for all elements.

  • In the functioning of all electricity-driven appliances, voltage is the cause and current is the effect.

  • If the distance between two points of the conductor increases, electrostatic field intensity decreases. The stronger the current, the more intense is the magnetic field.

Typical voltage


In India, the standard voltage at which power is transmitted to domestic residents is 230V with a frequency of about 50Hz. Batteries that are used for powering the remote control, flashlights provide 1.5V DC whereas batteries used in two-wheelers and other heavy vehicles are of 12V DC. The voltage used to power the railway locomotives through overhead lines is 50kV. The rate at which the power is transmitted from power stations is about 110 to 1200 kV which is several times greater than the domestic voltage. They are transmitted at high voltage in order to minimize power loss transmission.


See also:

  1. What is VLSI Technology?

  2. MOSFET Transistors

  3. Electric power

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