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PHYS-1500 PHYSICAL MODELING FALL 2006 Circuit Elements A resistor is familiar to most students of high school physics. Its symbol is: The potential difference (or voltage) across a resistor is proportional to the current passing through it. V = – iR, where i is the current, and R is the resistance. The minus sign means that the potential decreases in the direction that the current flows. A capacitor is symbolized by: The potential difference (or voltage) across a capacitor is proportional to the charge on it. V = – q/C, where q is the charge, and C is the capacitance. The minus sign means that the potential decreases in passing from the positively charged plate to the negatively charged plate. An inductor is symbolized by: The potential difference (or voltage) across an inductor is proportional to the rate of change of di current through it. V L , where i is the current, and L is the inductance. The minus sign dt means that the potential decreases in the direction of increasing current. A source of emf is often symbolized by: The longer parallel line indicates the side that is at higher potential (the positive side).