# Current source and capacitor in parallel

• fredro
In summary: But after that, there are other elements present and current can no longer flow through the capacitor.
fredro
I don't know if this is the right place to post this question, but here goes.

Whilst solving a circuit in class from a homework assignment, we arrived at a situation where a capacitor was in parallel with just a single independent DC current source. The question is, would current flow through the capacitor? The cap was charged (sequential switching situation) to 9.9 [V] beforehand. Many people in the class felt that the capacitor would allow current to flow even with no other circuit elements present. The source is ideal, by the way.

An ideal current source in parallel with a capacitor is a one of those situations that's best avoided unless there's something else in the circuitry to limit the duration that the connection is made or bypass the current! The reason is, the current source will continue to force current through the capacitor indefinitely, adding more and more charge to the plates. As a result, the voltage across the plates will continue to rise indefinitely also.

For ideal components the voltage would continue to rise linearly forever. For more realistic components the capacitor would shortly evolve into a ball of plasma and molten plastic and metal flying by your left ear when the manufacturer's stated maximum voltage limit is exceeded by egregious margins

fredro said:
Whilst solving a circuit in class from a homework assignment, we arrived at a situation where a capacitor was in parallel with just a single independent DC current source. The question is, would current flow through the capacitor?
It would. The current through the capacitor would be exactly what came from the DC source. For this reason, I would prefer to say they are in series, rather than parallel. On paper they might be drawn using neatly parallel pictorials, but electrically I'd call it a series connection of a capacitor and a current source.

Oh, BTW, I award you an extra half-mark for using "whilst".

Last edited:
NascentOxygen said:
It would. The current through the capacitor would be exactly what came from the DC source. For this reason, I would prefer to say they are in series, rather than parallel. On paper they might be drawn using neatly parallel pictorials, but electrically I'd call it a series connection of a capacitor and a current source.

Oh, BTW, I award you an extra half-mark for using "whilst".

I agree. I said parallel because in the circuit, they are in parallel. With the switches in the circuit, there exists a moment of time when they are the only two elements in the circuit.

I can provide a response to this question. In this situation, the capacitor and current source are in parallel, meaning they are connected to the same two points in the circuit. In this case, the capacitor does not allow current to flow through it, as the current source is an ideal source and can provide a constant current without any other circuit elements present. The capacitor acts as an open circuit in this scenario, as it has reached its maximum charge of 9.9V and cannot hold any more charge. Therefore, no current will flow through the capacitor in this situation. It is important to note that this is assuming ideal conditions and in a real circuit, there may be some small amount of current flow due to imperfections in the components.

## What is a current source and capacitor in parallel?

A current source and capacitor in parallel is a circuit configuration where a constant current source is connected in parallel with a capacitor. This means that the current source and capacitor have the same voltage across them, but the current is divided between them.

## What is the purpose of connecting a current source and capacitor in parallel?

The purpose of connecting a current source and capacitor in parallel is to create a circuit that can supply a constant current while also storing electrical energy in the capacitor. This is useful for applications that require both a steady current and energy storage, such as in power supplies and electronic filters.

## How does a current source and capacitor in parallel affect the voltage across the circuit?

In a current source and capacitor in parallel circuit, the voltage across the circuit is determined by the voltage of the current source. This is because the capacitor acts as an open circuit for DC current, so all of the current from the source flows through the capacitor. As a result, the voltage across the circuit remains constant regardless of the capacitance value.

## What happens when the value of the capacitor in a current source and capacitor in parallel circuit is increased?

When the value of the capacitor in a current source and capacitor in parallel circuit is increased, the amount of energy that can be stored in the capacitor also increases. This means that the capacitor can hold a larger charge and can discharge for a longer period of time. However, the voltage across the circuit remains constant as long as the current source remains the same.

## Can a current source and capacitor in parallel circuit be used for AC currents?

Yes, a current source and capacitor in parallel circuit can be used for both DC and AC currents. This is because the capacitor can block DC current while allowing AC current to pass through. In AC circuits, the capacitor and current source work together to create a phase shift between the voltage and current, which is useful in applications such as power factor correction.

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