How capacitor and inductor block DC?
Answer:
First off, a capacitor blocks DC and is a lower impedance to AC, while an inductor tends to block AC yet pass DC very easily. By "blocking", we mean than it offers a high impedance to the signal we're talking about.
First, though, we need to define a few terms to explain this. You know what resistance is, right? Resistance is the opposition to current flow that results in the burning of power, measured in watts. It does not matter if the current is AC or DC, the power dissipated by a perfect resistor is the same amount for either.
So resistance is one kind of "impedance" to current flow. There are 2 others - "inductive reactance", and "capacitive reactance". Both are also measured in ohms, like resistance, but both are different in that, for one thing, they vary with frequency, and for another, they don't actually consume power like a resistance does. So all together, there are 3 kinds of impedance - resistive, inductive, and capacitive.
The amount of blocking or impedance of inductors in ohms can be determined by:
XL = 2pi(f)L
Where 2pi is approximately 6.28,
f is the frequency (AC, obviously) of a signal,
L is the inductance measured in henries, and
where XL ("X sub L") is the inductive reactance in ohms.
Inductive reactance is the impedance of a component due to inductance; it is a kind of resistance, but does not actually burn power in watts like a resistor does, and since "f" for frequency needs to be supplied, the value of it varies with frequency for a given inductor.
Notice that as the frequency goes up, so does the impedance ( AC resistance) in ohms. And notice that if the frequency equals zero, then so does the impedance - a frequency of zero means DC, so inductors have virtually no resistance to DC current flow. And as the frequency goes up, so does the impedance.
Capacitors are the opposite- the formula for capacitive reactance is
XC = 1/(2pi(f)C)
Here, C is the capacitance of the cap in farads, "2pi" and "f" are the same as above, and XC ("X-sub-C") is the capacitive reactance in ohms. Notice that here, the reactance is "one divided by" the frequency and the capacitance - this results in values of impedance that go down with frequency and capacitance. So if the frequency is high, the impedance will be low, and if the frequency is near zero, which is DC, the impedance will be nearly infinite - in other words, capacitors block DC, but pass AC, and the higher the frequency of the AC signal, the less the impedance to it.
Block means "prevents the flow of"
Resistor has fewer free electrons as compared to a wire or a conductor and therefore it reduces the flow of current..it does not block it completely ...
Also mention whether you mean dc voltage or dc current..
block here may mean that some resistance is being provided to the current flow or the current is being interrupted by the device.
Inductor does not block DC it only blocks AC for some time and then reaches a maximum value and again conducts electricity. capacitor actually does not block DC as it just stores electric charges it just looks as if it is giving some resistance to the current.
Firstly,inductors block Ac and not DC.
When a DC current is applied across a capacitor, positive charge builds on one plate (or set of plates) and negative charge builds on the other. The charge will remain until the capacitor is discharged. When an AC current is applied across the capacitor, it will charge one set of plates positive and the other negative during the part of the cycle when the voltage is positive; when the voltage goes negative in the second half of the cycle, the capacitor will release what it previously charged, and then charge the opposite way. This then repeats for each cycle. Since it has the opposite charge stored in it each time the voltage changes, it tends to oppose the change in voltage. As you can tell then, if you apply a mixed DC and AC signal across a capacitor, the capacitor will tend to block the DC and let the AC flow through.
While a capacitor stores voltage as electrical energy, an inductor stores current as magnetic energy. Thus, a capacitor opposes a change in the voltage of a circuit, while an inductor opposes a change in its current. Therefore, capacitors block DC current and let AC current pass, while inductors do the opposite.
Here,block means it will not let ac/dc to pass through it.
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