# Node Voltage Current Direction

• CeilingFan
In summary, Kirchoff's Voltage Law and the Node Voltage Method can be used to determine the direction of current flow in a circuit. Current sources always flow in the direction of the symbol's arrow, and resistors dissipate power.
CeilingFan

## Homework Statement

Hi all, how do I know how the current direction are through each elements after solving a circuit (finding node voltages w.r.t GND)?

I think my understanding in electricity is rather incomplete. For example, I know that current should flow from a higher potential to a lower potential. However after solving with the node voltage method, I found out that, if you take a look at the bottom left of the image, that the current is flowing from GND to the left node (40V) through the current source. Does this not mean that the current is flowing from a lower potential now?

Assuming I've no knowledge of the mesh current method, how do I figure out the direction of current flow per circuit element?

## Homework Equations

Kirchoff's Voltage Law & Node Voltage Method.

## The Attempt at a Solution

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#### Attachments

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In a resistor, current flows from its higher potential end through that resistor to its low potential end. It is a resistor's potential difference that determines the magnitude of this current, according to Ohm's Law.

In a current source, current always flows in the direction of the symbol's arrow. For a current source, voltage across it is independent and is determined by the rest of the circuit.

In a circuit with multiple sources, the current into (or out of) any voltage source could be in either direction; the direction (as well as magnitude) is determined by other elements in the circuit.

NascentOxygen said:
In a resistor, current flows from its higher potential end through that resistor to its low potential end. It is a resistor's potential difference that determines the magnitude of this current, according to Ohm's Law.

In a current source, current always flows in the direction of the symbol's arrow. For a current source, voltage across it is independent and is determined by the rest of the circuit.

In a circuit with multiple sources, the current into (or out of) any voltage source could be in either direction; the direction (as well as magnitude) is determined by other elements in the circuit.

Hi. Thanks for the quick reply. Is there any fixed rule for which I can determine how it will move then?

I'm asking because I'm interested in knowing how to answer if, for example, the question requires me to determine if power is dissipated or generated through the elements (I do know that resistors always dissipate power, but what about current and voltage sources? From what I understand, if the current enters through the positive side of the voltage source it means a power dissipation? How do I know through which side the current enters i.e. direction?)

When a battery is delivering power to a circuit, current exits the battery from its + terminal.

If current is instead entering the battery through its + terminal, that represents power coming from the rest of the circuit, so to this voltage source it's sinking power (or, equivalently, sourcing negative power)

If the source happens to be a lead-acid battery, delivering negative power would mean it is being recharged.

NascentOxygen said:
When a battery is delivering power to a circuit, current exits the battery from its + terminal.

If current is instead entering the battery through its + terminal, that represents power coming from the rest of the circuit, so to this voltage source it's sinking power (or, equivalently, sourcing negative power)

If the source happens to be a lead-acid battery, delivering negative power would mean it is being recharged.

I have added in current directions and decided if power is dissipated or generated in my picture according to what I've understood from you. Is it correct?

#### Attachments

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Looks okay, but you overlooked one source. I think 'delivered' sounds better than 'generated'. They can be categorized as power sources and power sinks (or energy source vs. energy sink).

Thank you very much!

## 1. What is Node Voltage and Current Direction?

Node Voltage is the potential difference between two nodes in an electrical circuit. Current Direction refers to the flow of electric charge, which is typically from the positive terminal to the negative terminal.

## 2. How do you determine Node Voltage?

To determine Node Voltage, you can use Kirchhoff's Voltage Law (KVL), which states that the sum of all voltages in a closed loop is equal to zero. By setting up equations using KVL for each loop in the circuit, you can solve for the Node Voltages.

## 3. What is the importance of determining Node Voltage?

Determining Node Voltage is important because it allows us to understand the behavior of electrical circuits and analyze their performance. It also helps in troubleshooting and designing circuits for specific purposes.

## 4. How do you determine Current Direction in a circuit?

To determine Current Direction, you can use Kirchhoff's Current Law (KCL), which states that the sum of all currents entering a node is equal to the sum of all currents leaving that node. By setting up equations using KCL for each node in the circuit, you can solve for the Current Directions.

## 5. What are some common applications of Node Voltage and Current Direction?

Node Voltage and Current Direction are crucial concepts in the analysis and design of electrical circuits. They are used in various applications such as power distribution, electronic devices, and telecommunications systems. They also play a significant role in the development of renewable energy sources and electric vehicle technology.

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