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Need to know how to calculate series resistance, parallel resistance, and a combined series and parallel network? If you don't want to fry your circuit board, you do! This article will show you how in just a few easy steps. Before reading this, please understand that resistors do not actually have an "inside" and an "outside" to them. The use of "in" and "out" is merely a figure of speech to help novices understand the wiring concepts.
Steps
Help Calculating Resistance
Community Q&A
- QuestionHow do I calculate the supply current?
Community AnswerYou divide your total voltage by total resistance. For example let's say your voltage is 200V and your total resistance is 25 ohm, so it's IT=VT/ RT=200/25 = 8A. - QuestionHow do I connect a resistor to get the minimum resistance?Community AnswerNet resistance is minimum when all the resistors are connected in parallel.
- QuestionHow do I find the equivalent resistance between A and B arranged in a triangle?
Community AnswerSuppose A and B are the extremities of the base of the triangle. The resistor (R 1) between A and B would be parallel with the equivalent resistance of the other two, which are essentially in series. Then, R 2 and R 3 have an equivalent resistance: RE = R 2 + R 3. RE and R 1 are parallel, therefore the equivalent resistance is the reciprocal of the sum of the reciprocals of RE and R 1.
Video
Some Facts
- Understand resistance. Every material that conducts electrical current has resistivity, which is the resistance of a material to electrical current.
- Resistance is measured in ohms. The symbol used for ohms is Ω.
- Different materials have different resistance properties.
- Copper, for example, has a resistivity of 0.0000017(Ω/cm3)
- Ceramics have a resistivity around 1014(Ω/cm3)
- The higher the number, the greater the resistance to electrical current. You can see that copper, which is commonly used in electrical wiring, has a very low resistivity. Ceramic, on the other hand, is so resistive that it makes an excellent insulator.
- How you wire multiple resistors together makes much difference on the overall performance of a resistive network.
- V=IR. This is Ohm's law, defined by George Ohm in the early 1800s. If you know any two of these variables, you can easily calculate the third.
- V=IR: Voltage (V) is the product of current (I) * resistance (R).
- I=V/R: Current is the quotient of voltage (V) ÷ resistance (R).
- R=V/I: Resistance is the quotient of voltage (V) ÷ current(I).
Tips
- The equivalent resistance (Req) is always smaller than the smallest contributor for a parallel circuit; it is always greater than the greatest contributor for a series circuit.Thanks
- Calculate the resistance using the ohms law or the power law:Thanks
- Remember, when resistors are in parallel, there are many different means to an end, so the total resistance will be smaller than each pathway. When resistors are in series, the current will have to travel through each resistor, so the individual resistors will add to give the total resistance for the series.Thanks
- V = R * I- P = V * I we can replace V by RI so.....- P = RI * I- P = R I^2-Example: a lamp of 75watt lighted by a tension of 220 v, how to find its resistance? 1 - P = V * I - I = P/V => 75/220 = 0.34 ohm - P = RI^2 - 75W = R * 0.34^2 - R = 75/0.1156 = 648A- Let's check if it is the same with the other method.2 - V = R * I. - R = V/I - R = 220/0.34 = 647A almost the same ;).
References
- ↑ https://phys.libretexts.org/Bookshelves/University_Physics/Book%3A_University_Physics_(OpenStax)/Book%3A_University_Physics_II_-_Thermodynamics_Electricity_and_Magnetism_(OpenStax)/10%3A_Direct-Current_Circuits/10.03%3A_Resistors_in_Series_and_Parallel
- ↑ https://www.physicsclassroom.com/class/circuits/Lesson-4/Combination-Circuits
- ↑ http://physics.bu.edu/py106/notes/Circuits.html
- ↑ https://www.omnicalculator.com/physics/parallel-resistor
- ↑ https://www.electronics-tutorials.ws/resistor/res_5.html
- ↑ https://flexbooks.ck12.org/cbook/ck-12-physics-flexbook-2.0/section/17.5/primary/lesson/combined-series-parallel-circuits-phys/
- Handbook for Sound Engineers: The New Audio Cyclopedia, Glen Ballou, Editor
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