The online parallel circuit simulations on this page allow you to interactively understand how current, voltage, and equivalent resistance behave in a simple circuit. Through virtual setups with a power source, switch, bulbs, resistors, ammeters, and voltmeters, you can check the relationship between the circuit current, resistance values, and voltage drops at different points.
What are parallel electric circuits
Parallel circuits are characterised by their components being connected in such a way that they form multiple branches, each with its own path for current. In this type of setup, the voltage across each branch is the same, whilst the total current from the source is divided among the different branches according to the value of their resistances. The equivalent resistance is obtained by summing the reciprocals of each connected resistance. Parallel circuits are a basic and straightforward configuration that forms the foundation for analysing more complex arrangements.
Formula for equivalent resistance
When several resistors are connected in parallel, their combined effect on the circuit can also be expressed as a single equivalent resistance. In this case, the equivalent resistance is found by summing the reciprocals of each connected resistance, using the following formula:
1/Req = 1/R1 + 1/R2 + 1/R3 +…+ 1/Rn
The voltage applied to each branch is the same, whilst the total circuit current is shared among the different branches according to their respective resistance values. In this way, the equivalent resistance represents the total opposition to the flow of current in a circuit with multiple available paths.
Practical example
Suppose we have three resistors connected in parallel with values of 10 Ω, 20 Ω, and 30 Ω. The equivalent resistance of the circuit is found by adding the reciprocals of each resistance:
1/Req = 1/10 + 1/20 + 1/30 = 0,100 + 0,050 + 0,033 = 0,183
Req = 1/0,183 = 5,46 Ω
This means that, from the perspective of the power supply, the set of resistors behaves as a single resistance of approximately 5.46 Ω. The voltage applied to each branch is the same, whilst the total current supplied by the source is divided among the three resistors according to their values. For example, if the source provides 12 V, the currents will be 1.2 A through the 10 Ω resistor, 0.6 A through the 20 Ω resistor, and 0.4 A through the 30 Ω resistor, which adds up to a total of 2.2 A.
Parallel circuit simulations
Constant voltage
In this simulation, a circuit is built with a source, a switch, and a bulb and a resistor connected in parallel. A voltmeter is placed in each branch of the circuit to check that the voltage is the same in all of them and that it also matches the battery voltage. Change the resistance values and the battery voltage to verify that this property always holds in parallel connections.
Current distribution in parallel circuits
In this simulation, a circuit is built with a source, a switch, a bulb, and several resistors connected in parallel. A voltmeter is placed across the ends of the resistors. Additionally, ammeters are used in each branch and at the output of the source. Observe how the total current supplied by the battery is shared among the resistors in proportion to their value and how the sum of the partial currents matches the total current supplied by the source. Change the resistance values and the battery voltage to verify that this rule always holds.
Equivalent resistance in a parallel circuit
In this simulation, a circuit is constructed with a source, a switch, a bulb, and several resistors connected in parallel. A voltmeter is placed across the ends of the resistors and an ammeter to measure the total current supplied by the source. Calculate the equivalent resistance by measuring the total current and applying Ohm’s law (Req = V/I). Verify that the value obtained matches the result of adding the reciprocals of the individual resistances. Modify the resistance values and battery voltage to check that the rule always holds.
Branch independence
In this simulation, a circuit is built with a source, a main switch, and two branches connected in parallel: one with a bulb and another with a resistor. Each branch has its own switch. Observe how, when opening or closing any of the branch switches, the other continues to operate normally. The voltage in each branch remains constant, and only the total current supplied by the source changes. Change the resistance values and battery voltage to see how the total current varies without affecting the independent operation of each branch.
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Principles of Modeling, Simulations, and Control for Electric Energy Systems
Principles of Electric Circuits | 电路原理
Electrotechnique I
Electromagnetic Compatibility Essentials
