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Transcript
Grade 9 Science - Unit 4 – Physics – Electricity Potential Difference and Ohm’s Law Section 13.9 Pages 568-569 Potential Difference means the difference in potential energy per coulomb of charge at one point in the circuit compared to the potential energy per coulomb of charge an another point in the circuit. Potential energy is voltage. V=E/Q Where V = potential difference or voltage E = energy Q = amount of charge Question – If 42 J of chemical energy in a battery places 7.0 C of negative charge at the negative terminal, a deficit will occur at the positive terminal. What is the potential difference between the negative and positive terminals of the battery? Ohm's Law deals with the relationship between voltage (V) and current (I). The relationship states The potential difference (voltage) across an ideal conductor is proportional to the current through it. The constant of proportionality is called Resistance (R). Ohm’s Law is given by V = I R where V is the potential difference between two points which include a resistance (R). I is the current flowing through the resistance. Ohm’s Law states as the potential difference (Voltage) across a load (Resistance) increases, so does the current (Current). Ohm's Law can be used to solve simple circuits. A complete circuit is one that is a closed loop. It contains at least one source of voltage (thus providing an increase of potential energy) and at least one potential drop (i.e., a place where potential energy decreases). The sum of the voltages around a complete circuit is zero. An increase of potential energy in a circuit causes a charge to move from a lower to a higher potential (i.e., voltage). A fun Internet site to test your understanding of the Ohm’s Law relationship is http://jersey.uoregon.edu/vlab/Voltage/index.html