Parallel resistors are mostly known for having an equivalent of less resistance than any of the resistors that are connected in parallel. They also share the total heat (power) generation.
- 2 parallel resistors (R1 x R2)/R1+R2) = Rtotal
- 3 or more || (parallel) resistors 1/Rtotal = (1/R1) + (1/R2) + (1/R3)….
To keep things simple, I am just going to focus on equal value resistors, which simply have an equivalent resistance of… 1/2 for 2 || resistors, 1/3 for 3 || resistors, and so on. Explained in more detail below.
This lower resistance property will likely be confusing at first. So hopefully the diagram above helps clear things up. Each resistor is passing current based on the voltage across it. Therefore, if you add a second resistor in parallel that is the same value as the first one, they will have the same voltage across them, and they will both pass current as if the other one doesn’t exist.
Therefore, you will end up with twice the current to the rest of the circuit. That is how much current there would be if you had used a single resistor that was half the value of just one of the equal value parallel resistors.
Putting 5 volts across a 1KΩ resistor will provide 5V/1000Ω = 0.005A (5mA) of current. By connecting another 1KΩ resistor in parallel with that resistor, the second resistor will also have 5V across it, and therefore will also pass 5mA of current for a total current of 10mA. Since 5V/500Ω = 0.01A (10mA), we say that two 1000Ω resistors in parallel have the equivalent resistance of a single 500Ω resistor.
A really great benefit of parallel resistors is that the heat produced (voltage times current), is split up between the components. Therefore, each of 2 parallel 1K resistors with 5V across them, will get half as hot as a single 500Ω resistor with 5V across it.
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