What effect capacitor has on alternating current ac?

Answer 1

In the basic configuration, a capacitor is constructed with two parallel conductor plates with a layer of insulating material in between. When the cap is hooked up to the AC power supply, the voltage (v) across the plates and the charge (q) induced on the plates follow this capacitance expression:

C = dq/dv or i = C dv/dt, where C is determined by the properties of the insulating material and the geometry of the cap (in the case of the parallel plates, the separation between the two electrodes (t).

For the parallel plates, C can be written as (dielectric constant * plate area / t). Electrically, the change in the charge induced on the plates (dq), is directly related to the change in voltage difference (dv) between the two plates, since C is a constant. Theoretically, no energy is lost by charging and discharging the cap with an AC current. When the cap absorbs electrical energy from the power supply, it stores the energy in the electric field in the insulator. When discharging, the cap gives the stored energy back to the circuit -- hence, no energy loss.

In a circuit, we use the cap to prolong/smoothen/resist any voltage change in time or to absorb a sudden energy surge (electrostatic discharge and power-line glitches, for example).

Answer 2

A mnemonic that was taught in electrical school many years ago is ELI the ICEman. In an inductive circuit, the current through the inductor lags the voltage (E) (L) inductor (I) current.

In a capacitive circuit, the voltage through the capacitor lags the current (I) (C)capacitor (E) voltage.

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Answer 3

Capacitive reactance is -(2 pi f c)-1 in ohms, where f is hertz and c is farads. The leading negative sign means capacitive reactance, as opposed to inductive reactance. Essentially, at low frequency, the capacitor will look like an open circuit, and at high frequency, it will look like a short. For example, a 100 microfarad capacitor at 60 Hertz will have a reactance of -26.5 ohms, which means that current will lead voltage (because of the negative sign) and the impedance will be 26.5 ohms. The actual phase angle will depend on other factors such as resistance in the circuit.

Answer 4

A capacitor has uses in both AC and DC circuits.

A capacitor will block DC current when used in series, but allow an AC signal through.

A capacitor used in parallel across a power supply, can be used as storage, maintaining a level DC and conducting AC interference to ground.

Answer 5

It opposes the flow of current, due to its capacitive reactance (Xc). Capacitive reactance, measured in ohms, is inversely proportional to the frequency of the supply, and the value of capacitance. In other words, the greater the frequency or the capacitance, the lower the resulting capacitive reactance.

Answer 6

A purely capacitive load causes the load current to lead the supply voltage by 90 electrical degrees. In practise, however, there will always be some degree of resistance in a load, so we call such loads 'resistive-capacitive' (R-C), and the load current will lead the supply voltage by less than 90 elecrical degrees.

The capacitance of the capacitor causes it to oppose the load current due to its capacitive reactance (expressed in ohms) -which is inversely-proportional to the frequency of the supply voltage. The higher the frequency, the lower the capacitive reactance.

To summarise, a capacitor will act cause the load current to lead the supply voltage, and it will oppose the current due to its capacitive reactance.

Answer 7

A capacitor works by charging up with electricity in a certain amount of time. During this time, DC electrical current flows through the capacitor. But when it is charged as much as it can be, the dc electrical current stops flowing.

Answer 8

A capacitor draws a current that is 90 degrees or one quarter cycle ahead of the voltage. The instantaneous power moves into and out of the capacitor twice per cycle as it charges and discharges, and the average power over one cycle is zero.