![]() This allows you to solve for current once more: V/Rtot = 9 V/4.13 Ω = 2.18 A.ģ. You can now treat this portion of the circuit as a single resistive element with a resistance of 0.89 Ω, and the entire problem is solved as with a series circuit: Rtot = 1.125 + 2 + 1 = 4.13 Ω. Don’t forget to take the reciprocal of this number to get R! This is given by 1/0.89 = 1.13 Ω. This time, calculate the resistance in the parallel part of the circuit. Now imagine the same voltage and four resistors, but with the 1.5-Ω and 4.5-Ω resistors placed in parallel and the others arranged the same as before. In parallel circuits, which you’ll read about soon, the rule is: In a series circuit, the resistances of individual resistors are added together to calculate the resistance of the circuit as a whole. Where I is current in amperes (C/s), V is voltage, or potential difference, in volts (joules per C, or J/C note the energy term in the denominator) and R is the resistance in ohms (Ω). The previous section can be largely summarized by a simple mathematical law called Ohm’s law: ![]() The same device can usually be used as a voltmeter to measure potential difference. Current flow is measured using a device called an ammeter.Electric current comes in alternating current (a “jittery,” phasic flow) and direct current (uniform flow) forms the latter is the modern standard in use in electrical power grids. ![]() This is the potential difference or voltage referred to in physics, and its magnitude in part determines current flow in a circuit. Thus a “charge” (“positive” being implied unless stated otherwise) flows from areas of higher voltage to areas lower voltage. In this state, the charge has a higher electric potential than it does at some distance farther away. A positive charge placed near a positive terminal will experience “repulsion,” and “want” to move away from the terminal, all the more strongly as the distance closes to zero. The “unit charge” in physics is standardized as positive and has the same magnitude as the charge e on an electron. Since it is the flow of electrons that determines current, charges in a circuit flow away from the negative terminal and in the direction of the positive terminal. An electron by convention carries a negative charge with a magnitude of 1.60 × 10-19 coulombs, or C. Before exploring these, it’s necessary to look a little deeper, back to the idea of free electrons. The basic conceptual elements in the world of electricity are current, voltage and resistance. Most real-world examples are far more complex, however, and multiple types of electrical circuits exist, all of which are vital to the efficient flow of electricity. If they are given a closed-loop path in which to flow, an electrical circuit can be created.Ī simple circuit consists only of a source of voltage (electrical potential difference) a medium through which electrons can flow, usually a wire and some source of electrical resistance in the circuit. ![]() What’s going on inside all those wires, which themselves are mostly out of your sight? To start with the basics, free electrons will move in the presence of an electric field, for physical reasons that will be described later. ![]() The purpose of circuits is to get electricity and its considerable energy potential exactly where it needs to go, and to contain the potentially harmful effects of electricity in the process. ![]()
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