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Key Points on “electric potential” Electric Potential … • “electric potential” is used to refer to the voltage present on a point due to near by charges. They may ask for the “potential difference” as well. V=kq/d OR V=Ed OR V= E/q V is voltage K is constant E is electric field q is charge d straight line distance to test charge • Electric Potential and Potential Difference are most easily identified in a battery OR a circuit tied to a battery. The battery supplies the circuit with the same “potential” as listed. For example, a 9V battery has chemical potential to move charges (q) from the negative terminal to the positive terminal and out to the circuit. • Multiple charges in an area have the potential to influence a nearby charge. For example: What is the electric potential in volts at point If each of the represent a 3.5nC charge and are located at the corners of a 4cm by 4cm square? • Two disks, each with a radius if 1.5cm, are charged to ±0.885nC. What is the electric field strength of the capacitor? (this is a concept from chapter 26) What is the potential difference across the capacitor if the spacing between the disks is 2.5mm? • An electron with an initial speed of 800,000m/s is brought to rest by an electric field. What is the potential difference that stopped this electron? Key Points of “Electric Potential Energy” • Remember that potential energy is the result of the situation that is at hand. For example, a book on top of the side cabinet has higher potential energy than a book laying on the ground due to the “situation or position” it is in. • Charges can create “electric potential energy” because of the situation or arrangement they are in. If a charge is in a “voltage” situation….U=qV U is potential energy in Joules q is charge V is voltage • If there is not a “test charge” present, an area can still have electric potential energy due to the interactions of 2 or more charges. If these two + 2.6nCcharges are placed 5.5cm apart, their potential energy is based on charge value and distance of separation through the formula: U= kq1q2 /d • If there are more than 2 charges in an area, you must account for all charges and their influence on each other. If represents +3.0nC charge and represents a -1.5nC charge calculate the net potential energy in the following figure. Each leg of the triangle is 4.5cm • Watch for verbiage!!! Potential energy = Joules = U Electric potential = potential difference= voltage = V