2.  When two or more components are connected in a line, this is called a series connection (left of picture).  When they are connected across each other it is called a parallel connection (right of picture).  This module looks at how to calculate the combined resistance or capacitance of both of these connections.

3.  Let's start with resistors connected in series. The function of a resistor is to limit the flow of current. The bigger the resistance the more the current is limited.  When we connect two resistors together, each resistor limits the current in turn so the total resistance is more than either individual resistor.  The total resistance (Rt) is the sum of all the resistors: Rt = R1 + R2 + R3 +.... + Rn

4.  When resistors are connected in parallel, the current can flow down any of the resistors. This makes it easier for the current to flow and the overall resistance is decreased. If two equal value resistors are connected in parallel then the current splits evenly through them and the total resistance is half the individual value. As the values are normally different, we can use the following equation:

5.  Although this equation looks complicated, most calculators have a 1/x key or a reciprocal key. Suppose R1 = 100 and R2 = 50, then on a calculator you would enter:  100 followed by 1/x (= 0.01) 50 followed by 1/x (=0.02) Add the terms together 0.01 + 0.02 = 0.03 Finally press 1/x to give 33.3

6.  Capacitors are made of a pair of metal plates that hold charge, the bigger the plates the more charge they can hold. Effectively by connecting two capacitors in parallel we make one capacitor with bigger plates, which has a bigger capacitance. The total capacitance (Ct) is calculated by adding each of the capacitance's together:  Ct = C1 + C2 + C3 +... + Cn

7.  When capacitors are connected in series the overall capacitance is lower than the individual values. It is calculated in the same way as parallel resistors. The total capacitance (Ct) is: