The voltage of a capacitor cannot vary instantly. Capacitors, in general, resist voltage changes—they “want” their voltage to change “slowly”.

The derivative is not finite if the voltage changes from one value to another quickly (i.e. discontinuously). This means that an infinite current would be necessary to adjust the voltage quickly. Because an infinite current is not physically possible, the voltage cannot change instantly.

## How Do Capacitors Affect Voltage

The basic link between a capacitor and voltage and current is as follows: the amount of current flowing through a capacitor is determined by both capacitance and the rate at which the voltage rises or falls. A significant positive current will be induced through a capacitor if the voltage across it rapidly rises.

### How Does the Voltage of a Capacitor Change Over Time

The voltage V across the capacitance C capacitor is not independent of the charge Q on the capacitor. Q=CV is the relationship between them. As a result, for a given capacitance, the higher the charge, the higher the voltage.

The voltage between a capacitor’s plates is the work per unit charge required to transport the charge between the two plates. As the charging source (e.g., battery) moves more charge Q between the plates, the voltage V rises. And it falls when the capacitor discharges over time.

## Does the Voltage Across a Capacitor Alter Instantly?

Capacitors respond to voltage changes by supplying or draining current in the opposite direction of the change. When exposed to increasing voltage, a capacitor serves as a load, drawing current as it absorbs energy (current going in the negative side and out the positive side, like a resistor).

The above calculation illustrates the equations of voltage and current across a capacitor. We can see that, for the voltage to change instantaneously, the current through the capacitor has to be infinite. This isn’t possible. Hence capacitor resists any instant change in voltage.

### Can There Be an Instantaneous Current Change Across a Capacitor

Yes, it is possible. When a capacitor charges or discharges, the current in it fluctuates abruptly, depending on the capacitor’s resistance. In general, any sudden voltage shift at the capacitor terminals causes a sudden current change.

The current flowing through the capacitor is related to the rate of voltage change across it. The direction of current flow is the only distinction between the effects of reducing and increasing voltage.

### Does Voltage Stay Constant in a Capacitor

No, the voltage across a capacitor doesn’t remain constant. The current flowing through the capacitor is related to the rate of voltage change across it. The direction of current flow is the only distinction between the effects of reducing and increasing voltage.

The voltage reduces as you discharge a capacitor. This is because the charge stored in a capacitor is proportional to the voltage for a given capacitance (Q=VC). The charge on the capacitor decreases as you discharge it, and so the voltage decreases. Similarly, the voltage will increase when the capacitor is charging.

## Why Capacitor Does Not Allow Sudden Change of Voltage

The capacitor does not enable sudden voltage changes since these changes occur in zero time, resulting in an infinity current, which is not feasible due to the following reasons:

- The capacitor isn’t ideal, and the circuit linked to it (which must be a short circuit) isn’t ideal. Hence the superconducting impedance isn’t zero.
- Even if the first case is full, the electrons in the capacitor have mass, a limited number of them, they cannot accelerate quickly, and the current cannot be unlimited.

A capacitor can only discharge at a certain current rate. It takes some time for him to discharge himself. Because the voltage is proportional to the charge, it will change slowly in time with the passing current

### What Happens When the Voltage Across a Capacitor Changes Instantaneously

When there is a quick shift in voltage across an ideal capacitor, the following is true:

- When an abrupt change happens, the capacitor functions as a short circuit (a piece of wire).
- The capacitor begins charging immediately once the abrupt transition is over.
- If the voltage across the capacitor remains constant for an extended period of time, the capacitor will behave as an open circuit.

Here are some more properties of capacitors exposed to abrupt voltage shifts.

- When there is a quick change in voltage, big capacitors can absorb a great quantity of current.
- Large currents can damage other components in some cases (especially semiconductors). When there is a sudden shift in voltage, capacitors can supply a high amount of current.

## Which Type of Capacitor Can Pass a Huge Amount of Current in Series

Capacitors do not conduct direct current or alternating current. The charge is stored at a potential difference between two sites separated by a dielectric barrier (insulator). For high currents and voltages, a capacitor with high capacitance and dielectric strength will be required. Defibrillator capacitors carry strong currents. Their specifications are:

Voltage (DC): up to 6,000 VDC

Stored Energy: Up to 500 J

Capacitance: up to 500 µF

Energy Density: Up to 2.0 J/cc

Peak Current: Up to 300 A

### Why doesn’t the capacitor act like zero ohms when sudden voltage changes occur?

Inductance is a property of real capacitors. When abrupt changes occur, this inductance prevents the capacitor from operating at zero ohms. Because ceramic capacitors and mica capacitors have low inductance, they behave virtually like zero ohms during abrupt voltage changes. Tubular capacitors have larger inductance.

## Conclusion

If we charged a capacitor from a source with no resistance, the voltage would change instantly. Similarly, a charged capacitor would discharge instantly across an ideal short circuit. However, because resistance is always present in real-world circuits, the voltage in a real capacitor does not change instantly.

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