By applying the concept of series and parallel circuits, Karen shows you how to combine a pair of resistors, using Ohms law to calculate the resistance needed to supply the proper voltage to a diode. Karen illustrates Ohm’s Law by making a simple circuit on a breadboard. To do this she uses two sources of power: a 2- AA battery pack that supplies 3 Volts and a 4 - AA battery pack that supplies 6 Volts to create a circuit that powers a red LED. Karen supplies 6 volts to the LED and demonstrates how it’s not a good voltage for it. If you want to use a 6 volt battery pack but don’t want to damage or burn out your LEDs you’ll need to add resistors to your circuit. In order to figure out how, you need to look at Ohm’s law. Ohm’s Law describes the relationship between voltage current and resistance. You use V for voltage (measured in VOLTS), I for current (measured in AMPS), and R for resistance, measured in OHMS). Current is measured in AMPS, named for a French mathematician Andre-Marie Ampere, the I originates from the French phrase for current intensity, intensite de courant. While current intensity has been shortened to just current, it is still represented by I for intensity. To make things easier to understand, Karen compares relationship between voltage, current, and resistance to water flowing through a pipe. Using this analogy, voltage is like water pressure, pushing the electricity through the circuit. Current is the amount of water flowing through the pipe. Resistance is the size of the pipe, which determines how much the flow is restricted. If the pressure (the voltage) stays the same and the resistance increases, making it more difficult for the water to flow, then the flow rate (or the current) must decrease. According to Ohm’s law, you need three variables: voltage, resistance, and current. To solve for resistance, you’ll need to find the voltage and current. The red LED is rated for 2.1 volts and 20 milliamps. In order to make