Your desk lamp, fridge, TV and all other electrical appliances require the flow of electrons within a circuit to actually function. Circuits are one of the most game changing inventions, allowing humanity to be powered by the next power source: electricity. This article will introduce you to the fundamentals of the components of a circuit, how it works and how to determine different statistics of a circuit.
Inside a circuit
The first step to grasp the knowledge of circuits would be understanding what’s actually going on inside them. Within a circuit, electrons are essentially pushed in a direction by an electric field . Scientists decomposed this process with three units: Voltage, Current and Resistance.
Current
Current refers to the rate of flow of electric charge.
Essentially, current refers to the amount of charge that is being pushed at a point in a circuit.
Mathematically we could denote this as q/t where q refers to the amount of charges (Coulombs) and t is in seconds.
Coulombs is the SI unit to denote the amount of electron to form a charge.
1 Electron in conventional current is about 1.6 x 10-19 (coulombs) OR 1 coulombs is about 6.25 x 1018 electrons.
The unit of Current is in Amperes or “amps” (A).
Voltage
Voltage refers to the potential difference between two points in a circuit.
In other words, Voltage refers to the magnitude of charges being “pushed” in a circuit.
In physics terms, Voltage refers to the amount of work done per charge.
This mathematically denoted as W=qV (Work = charge x Voltage)
The unit for Voltages is Volts (V)
Resistance
Similar to its name, Resistance refers to the ratio of current that is opposed to the flow.
Generally through forcing the electrons to collide with particles inside the conducting wires, Resistance transforms electrical energy into heat energy in diminishing the magnitude of charges in a circuit.
You could think of resistance as the “level of difficulty” for electrons to pass through of circuit
Mathematically we could formulate resistance as R = pl/A
R - Resistance measure in SI units “Ohms” (Ω)
p - The resistivity of the conductor’s material.
l - The length of the conductor. (Generally wires).
A - The cross sectional Area of the conductor.
Ohm’s Law
Published by German Physicist Georg Ohm, Ohm’s Law states that the electric current through a conductor between two points is directly proportional to the voltage across the two points, which the constant proportionality is referred to as the Resistance. This results in the famous equation V=IR, which is extremely useful in deducing one component of a circuit given the others. To find out more about Ohm’s law, please click here.
Circuit Diagrams
There are numerous components that could be placed in a circuit, each with a different use and symbol. Most importantly, for a functioning circuit you would need a power source, a control terminal and at least one component that provides some resistance (Components such as lamps, ammeters and resistors all have resistance). If there is no resistance in a circuit, then a phenomenon known as a “short circuit” will occur, where theoretically, an infinite amount of current is passed through. This all transfers into heat energy, the circuit to ignite.
Here are some common circuit components:
Parallel and Series Circuits
Circuits are linked either in series or parallel and based on its formation, the properties of Voltage, Current and Resistance differ.
Within a series circuit:
Current is the same throughout.
Voltage would be proportional to the resistance.
Within a Parallel circuit:
Voltage is the same throughout.
Current will be shared between different paths at a junction in proportion to the resistance.
Works Cited
BBC Bitesize (2021). Introduction to circuits - Electricity - KS3 Physics - BBC Bitesize. [online] Available at: https://www.bbc.co.uk/bitesize/articles/zjm8kty#z46yydm [Accessed 1 Sep. 2024].
Britannica (2019). Resistance | electronics | Britannica. In: Encyclopædia Britannica. [online] Available at: https://www.britannica.com/technology/resistance-electronics.
Fluke (2023). What is Voltage? [online] www.fluke.com. Available at: https://www.fluke.com/en-au/learn/blog/electrical/what-is-voltage.
Wikipedia Contributors (2019). Ohm’s law. [online] Wikipedia. Available at: https://en.wikipedia.org/wiki/Ohm%27s_law.
www.education.vic.gov.au. (n.d.). Electric circuits. [online] Available at: https://www.education.vic.gov.au/school/teachers/teachingresources/discipline/science/continuum/Pages/electriccircuit.aspx.
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