Experiment 6
VOLTAGE-CURRENT CHARACTERISTICS

PRELAB

PURPOSE

To study the characteristics of voltage and current in a battery powering an ohmic (linear) circuit element and two non-ohmic (non-linear) circuit elements.

MATERIALS   digital multimeter, ammeter, component box, dc power source.

RELEVANT EQUATIONS

 Ohms' law DISCUSSION Figure 6-1: A Simple Resistive Circuit

Fig. 6-1 shows an ideal battery; that is, a battery with no internal resistance. This power source is connected to a circuit element of resistance R. The resistance of a circuit element is defined as where V is the potential drop across the circuit element, and I is the current through the circuit element. The unit of resistance, volts per ampere, is also called the ohm (Ω). If the resistance is constant for all values of I the circuit element is said to be ohmic. For an ohmic circuit element a graph of I vs. V will be a straight line through the origin (Fig. 6-2a) with slope of ΔI/ΔV or 1/R, which is a constant. The ideal battery in Fig. 6-1 produces a constant potential difference across its terminals independent of the current being delivered to the load R and has the V-I graph shown in Figure 6-2b. Figure 6-2: Voltage-Current Characteristics

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