Ohm's law applies at each resistor (and this is where the AC analysis gets more complicated). KVL applies around each mesh, because the algebraic total of all voltages around the loop must equal zero. the algebraic sum of all currents going "in" must be zero). KCL applies at each node, because the total of all currents "in" and all currents "out" of that node, must be equal (i.e. But for DC circuits, the three basic laws that always apply are Ohm's Law, Kirchoff's Current Law (KCL) and Kirchoff's Voltage Law (KVL). For changing signals there are AC circuit analysis techniques. This is a DC circuit because the node voltages and mesh currents are steady, and do not change. The same current flows through all of these components. The mesh current i flows through BAT1, R1, and R2.
There is one mesh loop (a mesh is a "loop that has current"): This is a lumped-constant model, so we're ignoring the minor effects of wiring resistance and inductance, and just assuming that the voltage is the same along the entire length of a wire. Node voltage V3 is the voltage at one terminal of R2 and at BAT1(-) terminal. Node voltage V2 is the voltage at one terminal of R1 and one terminal of R2. Node voltage V1 is the voltage at BAT1(+) terminal. There are three nodes (a node is a "place that has voltage"): Simulate this circuit – Schematic created using CircuitLab I've redrawn your schematic in conventional form, with the energy flowing from left to right and the higher voltages towards the top. So you can't label a node "5V 1A", you can only label the node "5V". In your first schematic, the nodes are mislabeled - there is no such thing as a node current.
In this case, you go up 5 volts in the battery, then you come down 2.5 volts in each resistor, ending up at zero right where you started. The voltages around the loop must also add up to zero ('what goes up must come down'). The current must be the same at all points along that path as charges cannot be created or destroyed ('what goes in must come out'). Since there are two 1 ohm resistors in series, the voltage across the pair is 1 + 1 = 2 volts.
#Ipass black power voltage series
How about applying 1 A to two series 1 ohm resistors? Well, that 1 A is going to produce V = 1 A * 1 ohm = 1 volt across each resistor. Then the voltage across each resistor is V = 2.5 * 1 = 2.5 volts. V = I * R tells us that 5 = I * 2 where I = 2.5 A. Total resistance of two 1 ohm resistors in series is 1 + 1 = 2 ohms. This 5v is applied across two 1 ohm resistors in series. Since you have a batery symbol drawn, I will assume you are applying 5 volts. Either you are applying 5V or you are applying 1A. You can't specify the current AND the voltage. In simpler terms, applying to your circuit with one power source, this means that the sum of the voltage drops across the resistors in the circuit must equal the supply voltage. Kirchoff's Voltage Law states that the algebraic sum of the voltages around a series circuit must equal zero. From Ohm's Law, this will result in a current of 2.5 amps, and a voltage drop of 2.5 volts across each resistor. In the first circuit you have a total resistance of 2 Ohms, and (I assume) a power supply of 5 volts. KCL means that the current will be the same at all points in a simple series circuit, so your first circuit (with 1 amp at one point, and 5 amps at another) is impossible. In plain English, this means that all the current that arrives at a point in the circuit must leave that point (and no more current can leave than arrives.) If KCL was not true, charges could build up at one point in the circuit, leaving none to flow elsewhere, so a circuit would only operate briefly, until there was no charge available to flow. Kirchoff's Current Law (KCL) states that the algebraic sum of the currents at any point in a circuit must equal zero. I consider Kirchoff's Laws as scientific wording of what should be common-sense observations - unfortunately, common sense isn't as common as we might like, so we have to spell these things out. There are two fundamental laws of electricity that you must always keep in mind - Kirchoff's Current Law, and Kirchoff's Voltage Law.
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