Tham khảo tài liệu 'sat ii physics (gary graff) episode 1 part 8', ngoại ngữ, ngữ pháp tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | CHAPTER 5 Series and Series Parallel Circuits A source of electrical potential sometimes has a single task such as to operate a flashlight bulb. But just as often the power source is used to perform many tasks through several different pathways. The first example we will discuss is the single task or series circuit and the second type is called a parallel circuit. Series Circuits Series circuits have only one pathway in which current can flow. Every unit of charge flowing in a series circuit must pass through every position of the circuit. When more than one resistor is in a series circuit the value of each resistor is added together to give the total resistance. Rt R1 R2 R3 R. The total resistance for the circuit shown is 12Q. Rt 2Q 4Q 6Q Rt 12Q Peterson s SATIISuccess Physics ELECTRIC CIRCUITS Parallel Circuits Parallel circuits have two or more pathways through which current can flow. The total value of the current depends on the parallel resistance offered against the current flow. Since current and resistance are indirectly related the highest resistance will allow less current to flow and the lowest resistance will allow more current to flow. The total resistance of a set of parallel resistors is found in the following manner 1 Rt R1 R2 R 3 1 1111 __ -- -- -- Rt 2Q 5Q 10Q 40Q 4 .5Q .2Q .1Q .025Q Rt 4 .825 Rt Rt The value of the final resistance shows another characteristic of parallel resistances. The total resistance of a set of parallel resistors is always equal to or less than the value of the smallest resistor in the parallel set. When an extremely large resistor 500 meg-ohms is Peterson s CHAPTER 5 in parallel with an extremely small resistor the total resistance is equal to the smallest resistor. When a set of parallel resistors are all of equal resistance we can divide the resistance value of one of them by the total number of resistors in parallel to find the resistance of the parallel system. Example Let s do a problem .
