Resistors are said to be connected together in parallel when both of their terminals are respectively connected to each terminal of the other resistor or resistors. Of course, there are some differences between a resistor in series and parallel circuits. In this post, we will have a look at resistors in parallel.
Unlike a series resistor circuit, in a parallel resistor network, the circuit current can take more than one path as there are multiple paths for the current. Then parallel circuits are classed as current dividers.
Since there are multiple paths for the supply current to flow through, the current may not be the same through all the branches in the parallel network. However, the voltage drop across all of the resistors in a parallel resistive network IS the same. Then, Resistors in Parallel have a Common Voltage across them and this is true for all parallel-connected elements.
So we can define a parallel resistive circuit as one where the resistors are connected to the same two points (or nodes) and are identified by the fact that it has more than one current path connected to a common voltage source. Then in our parallel resistor example below the voltage across resistor R1 equals the voltage across resistor R2 which equals the voltage across R3 and which equals the supply voltage. Therefore, for a parallel resistor network this is given as:
In the following resistors in parallel circuit the resistors R1, R2 and R3 are all connected together in parallel between the two points A and B as shown.
Parallel Resistor Circuit
In the previous series resistor network we saw that the total resistance, RT of the circuit was equal to the sum of all the individual resistors added together. For resistors in parallel the equivalent circuit resistance RT is calculated differently.
Here, the reciprocal ( 1/R ) value of the individual resistances are all added together instead of the resistances themselves with the inverse of the algebraic sum giving the equivalent resistance as shown.
Resistors in Parallel Summary
So to summarise. When two or more resistors are connected so that both of their terminals are respectively connected to each terminal of the other resistor or resistors, they are said to be connected together in parallel. The voltage across each resistor within a parallel combination is exactly the same but the currents flowing through them are not the same as this is determined by