Resistor series-parallel circuit is a combination of a series circuit of a resistor circuit and the resistor of the parallel circuit.
Figure 1-22 is a parallel circuit comprising a resistor string 3 constituted of the resistor. Resistors R1 and R2 parallel circuit, and then connected in series with resistor R3, which is purely resistive series-parallel circuit.
1-22 resistor series-parallel circuit composed of a resistor 3
important hint
Pure resistance series-parallel circuit may also have other forms of circuitry, there may be more resistance series-parallel. Characterized in that the series-parallel circuit, the circuit portion of the resistance in parallel and then in series with the other resistances. In addition to the resistor series-parallel circuit may be configured, various other components can constitute a series-parallel circuit, series-parallel circuit of a resistor series-parallel circuit is essential.
1. The total resistance of the resistor series-parallel circuit characteristics
Series-parallel circuit having some common characteristics of the parallel circuit and series circuit.
The resistor series-parallel circuit, the total resistance equal to the parallel circuit of the parallel resistance value of each resistor in series with the sum of the other. After such circuits R1 and R2 in parallel, and then connected in series with the resistor R3, as shown in Figure 1-23 is a schematic view of an equivalent procedure.
1-23 schematic diagram of an equivalent procedure
important hint
When the need to calculate the total resistance of the series-parallel circuit (often not necessary to calculate the resistance in the circuit analysis), for convenience, to calculate all the parallel resistance of the parallel resistor, in series then calculated.
2. resistor series-parallel circuit current characteristics
Figure 1-24 is a resistor series-parallel circuit shown, the total current in the circuit is I, a current flows through the resistor R1 is I1, a current flowing through the resistor R2 is I2, the current flowing through the resistor R3 is I3, the circuit the total current I through the resistors R1 and R2, and then flows to the ground terminal via the resistor R3. Circuit, the total current I = I1 + I2 = I3.
FIG schematic 1-24
3. A series-parallel circuit voltage characteristic of the resistor
As shown in Figure 1-25, the voltage U1 across the resistor R1 and R2, U2 equal to the voltage across the resistor R3 to U3, and the voltage on R1 and R3 is equal to voltage + V.
FIG schematic 1-25
Such a problem occurs in the circuit analysis, that is, when the resistor R1 in the circuit is open, the voltage across the resistor R3 is increased or decreased. After the analysis of this problem is the key to see an open circuit the resistor R1, the current flowing through the resistor R3 is increased or decreased, because the current times the resistance value of the resistor is equal to the voltage across the resistor flows, the resistance value R3 is an open circuit R1 before and after the open circuit is unchanged.
Since the current flowing through the resistor R3 is the total current of the circuit, while the constant voltage + V (+ V in the circuit does not change), the total resistance of the circuit determines the size of the magnitude of the current in the circuit. Thus, analysis of this problem becomes the string of change in the total resistance of the parallel circuit of R1 before and after open.
Open before the resistor R1, R1 and R2 are connected in parallel, so that the total resistance of the parallel circuit is reduced, only the resistor R2, compared with the original parallel resistance of R1 and R2 when R1 is left open, the resistance value is increased. It can be seen, the total resistance R1 is left open after this string of the parallel circuit is increased, so that the total current string of the parallel circuit is reduced, to reduce the current flowing through the resistor R3, the voltage at R3 Save small.
Analysis Conclusion
After the analysis of the resistor R1 on the open circuit voltage of the resistor R3 is increased or decreased, a step is carried out, throughout the analysis, the use of the various circuit characteristics stated before, the analysis is such a circuit for each of various kind of circuit characteristics together using the process.
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