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How to independently check malfunction of parallel resistance circuit? Chart details
2023-04-04【Archive】
Parallel resistance circuit is simplest parallel circuit, and all responsible circuits can be converted into resistor series circuit and resistance parallel circuit to understand working principle. The characteristics of parallel circuits and series circuits are completely different, and they are completely different circuits, and they cannot be equivalent to each other (resistance parallel circuit circuit).
The figure shows a parallel resistor circuit. It can be seen from figure that terminals R1 and R2 of resistor are connected respectively, forming a parallel circuit of two resistors. +V is DC operating voltage of this circuit. When R1 and R2 are connected in parallel and circuit is operating in an AC circuit, shape of circuit remains unchanged, except that DC voltage +V is changed to an AC signal. When analyzing parallel resistor circuits, you need to understand following characteristics of parallel resistor connections.
01
The characteristic that total resistance of a parallel circuit becomes smaller and smaller is directly opposite to total resistance of a series circuit. If two 20 kΩ resistors are connected in parallel, total resistance after parallel connection is half resistance of one 10 kΩ resistor. as shown below. After parallel connection, total resistance is R
Note:In a parallel circuit of resistors, reciprocal of total resistance R after each resistor in parallel is equal to sum of reciprocals of each resistor in parallel, formula: 1/ R=1/R1+1/R2+1/R3......
02
The total current of parallel circuit is equal to sum of currents of each branch (principal diagram of current of each branch of parallel circuit)
As shown in figure, current I1 flowing through resistor R1, current flowing through resistor R2 is equal to I2, total current I of parallel circuit, current flowing from +V power supply is divided into two paths, one path passes through resistor R1 and other path is through resistor R2, sum of branch currents is equal to total current in circuit, for this particular circuit it is I=I1+I2. If there are more parallel branches, then I=I1+I2+I3... In a branch of a parallel circuit, current value in branch is same as resistor in branch. The resistance value is inversely proportional to size of resistor. A resistor with a large resistance value has a small current in circuit. Conversely, a resistor with a low value of resistance has a large current in circuit.
From formula I=U/R, you can find out that when current of resistor R1 is less than current flowing through R2, as shown in figure below:
Parallel current characteristic memory circuit:
Using image of a river, water flowing from reservoir is divided into three paths, each of which flows into sea, which is equivalent to current flowing from power source flowing into each branch of resistance circuit.
03
Equal Voltage Characteristics at Both Ends of Parallel Resistors In a parallel circuit, voltages across each parallel resistor are equal (as shown in figure below). Since two resistors R1 and R2 are connected in parallel, voltages across them are equal. If more resistors are connected in parallel in a circuit, voltage across each parallel resistor will be same.
04
The main contradiction in a parallel circuit is small resistance of parallel resistance circuit.If resistance value of a particular resistor is much larger than resistance value of other resistances, resistance will not play a big role and can be considered open. This leaves a small resistor in circuit. When analyzing a parallel circuit, it is necessary to understand low resistance resistor, which is main contradiction in this circuit, even if low resistance resistor plays a major role in parallel circuit, which is complete opposite of series circuit.
05
Resistive parallel circuit open circuit and short circuit detection method:
1) The open circuit detection method is as follows:
When circuit is disconnected, use a multimeter to measure total resistance of parallel circuit. Under normal conditions, measured total resistance should be
If measured resistance value is greater than either of R1 and R2, it means that R1 or R2 is open in circuit. In particular, it is necessary to analyze which circuit is open, or current of each resistance branch can be determined. measured way to judge.
2) The short circuit detection method is as follows:
If measured total resistance is zero, it means that a short circuit has occurred in parallel circuit. If you need to know exact location and cause, you need to take additional measurements. This is of great importance for troubleshooting as extent of faulty circuit can be determined as well as direction of test.
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