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LAB 4: KIRCHHOFF’S RULES DIY Lab This section is adapted from reference 1. Objective In this experiment, you will experimentally verify Kirchhoff’s rules by measurement and by mathematical analysis. Apparatus (Lab Kit* or NIC Lab) 5 resistors  one 6V battery or power supply (each under 1.5 kΩ each, not all equal)  digital multimeter  12 connecting wires *If you do not have the Lab Kit, you can use equivalent items. Contact your instructor regarding equivalent items to ensure that the objective of this experiment is maintained. Introduction The most basic of electrical circuits contains a single resistor connected to the terminals of a battery. This is a complete circuit, forming a continuous path between the battery terminals. The resistor is called the load and the battery is the source of emf. We assume that all wires used as connectors are ideal, with Rwire  0 . In analyzing a circuit, we make use of a representation of the circuit termed a schematic. You are already familiar, after experiment the Basic Electric Circuits Lab, with the representation of resistors and batteries; the only new symbol we introduce is that of the node, shown in Figure 4.1 below. It is simply a point where the current divides or joins. We are now ready to analyze circuits. To analyze a circuit we do two things: 1. find the current in each component, and 2. find the potential difference across each component. The rules of circuit analysis are called Kirchhoff’s rules. The Loop Rule This rule asserts that the net change in electric potential around any closed loop in a circuit is zero. This is a statement of energy conservation, since a charge that moves around any closed DIY First-Year Physics Laboratory 

Kirchhoff’s Rules path and returns to its original point must have no change in potential energy. If we apply this conservation law to a closed loop in a circuit, then

 V  0 , where V is the potential difference across each component in the loop as measured while

References: 1. Laboratory Manual for PHY 100 & 101 Introductory Physics I and II and PHY 120 & 121 Principles of Physics I and II, 5th Edition 2004, prepared by Jason Diemer, North Island College. DIY First-Year Physics Laboratory 9