Do you want to learn how to calculate a resistor in series, in parallel, or a resistor network in series and in parallel? If you don't want to blow your circuit board, you better learn! This article will show you how to do it in simple steps. Before starting, you need to understand that resistors have no polarity. The use of "input" and "output" is only a way of saying to help those who are not experienced in understanding the concepts of an electrical circuit.
Steps
Method 1 of 3: Resistors in Series
Step 1. Explanation
A resistor is said to be in series when the output terminal of one is connected directly to the input terminal of a second resistor in a circuit. Each additional resistance adds to the total resistance value of the circuit.
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The formula for calculating the total of n resistors connected in series is:
R.eq = R1 + R2 +… R
That is, all the values of the resistors in series are added together. For example, calculate the equivalent resistance in the figure.
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In this example, R.1 = 100 Ω and R.2 = 300Ω are connected in series.
R.eq = 100 Ω + 300 Ω = 400 Ω
Method 2 of 3: Resistors in Parallel
Step 1. Explanation
Resistors are in parallel when 2 or more resistors share the connections of both the input and output terminals in a given circuit.
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The equation for combining n resistors in parallel is:
R.eq = 1 / {(1 / R1) + (1 / R2) + (1 / R3) … + (1 / R)}
- Here is an example: R data1 = 20 Ω, R.2 = 30 Ω, and R.3 = 30 Ω.
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The equivalent resistance for the three resistors in parallel is: R.eq = 1/{(1/20)+(1/30)+(1/30)}
= 1/{(3/60)+(2/60)+(2/60)}
= 1 / (7/60) = 60/7 Ω = approximately 8.57 Ω.
Method 3 of 3: Combined Circuits (series and parallel)
Step 1. Explanation
A combined network is any combination of series and parallel circuits connected together. Calculate the equivalent resistance of the network shown in the figure.
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The resistors R1 and R2 they are connected in series. The equivalent resistance (denoted by Rs) And:
R.s = R1 + R2 = 100 Ω + 300 Ω = 400 Ω;
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The resistors R3 and R4 are connected in parallel. The equivalent resistance (denoted by Rp1) And:
R.p1 = 1 / {(1/20) + (1/20)} = 1 / (2/20) = 20/2 = 10 Ω;
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The resistors R5 and R6 they are also in parallel. The equivalent resistance, therefore, (denoted by Rp2) And:
R.p2 = 1 / {(1/40) + (1/10)} = 1 / (5/40) = 40/5 = 8 Ω.
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At this point, we have a circuit with resistors R.s, Rp1, Rp2 and R7 connected in series. These resistances can be added together to give the equivalent resistance Req of the network assigned at the beginning.
R.eq = 400 Ω + 10 Ω + 8 Ω + 10 Ω = 428 Ω.
Some facts
- Understand what a resistance is. Any material that conducts electric current has a resistivity, which is the resistance of a given material to the passage of electric current.
- Resistance is measured in ohm. The symbol used to denote ohms is Ω.
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Different materials have different strength properties.
- Copper, for example, has a resistivity of 0.0000017 (Ω / cm3)
- Ceramic has a resistivity of about 1014 (Ω / cm3)
- The higher this value, the greater the resistance to electric current. You can see how copper, commonly used in electrical wiring, has a very low resistivity. Ceramic, on the other hand, has such a high resistivity that it makes it an excellent insulator.
- How multiple resistors are connected together can make a big difference in how a resistive network works.
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V = IR. This is Ohm's law, defined by Georg Ohm in the early 1800s. If you know two of these variables, you are able to find the third.
- V = IR. The voltage (V) is given by the product of the current (I) * the resistance (R).
- I = V / R: the current is given by the ratio between the voltage (V) ÷ resistance (R).
- R = V / I: the resistance is given by the ratio between the voltage (V) ÷ current (I).
Advice
- Remember, when resistors are in parallel, there is more than one path to the end, so the total resistance will be less than that of each path. When resistors are in series, current will have to pass through each resistor, so the individual resistors will add together to give the total resistance.
- Equivalent resistance (Req) is always smaller than any component in a parallel circuit; is always greater than the largest component of a series circuit.
