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Why does an inductor offer high impedance to ac but very low impedance to dc?
Wiki User
∙ 12y ago
Because an inductor resists a change in current. The equation of an inductor is ...
di/dt = V/L
... meaning that the rate of change of current is proportional to voltage and inversely proportional to inductance. Solve the differential equation in a sinusoidal forcing function and you get inductive reactance being ...
XL = 2 pi f L
Wiki User
∙ 12y ago
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Why fault current can be extremely high?
Because the impedance to current flow is very low.
What effect does transformer has a very low impedance on short circuit current?
the short ckt curent will be very high.
Why PT Burden is always higher than CT Burden?
PTs are high voltage, low current transformers and so need a relatively high impedance (or burden) load to function accurately. CTs are high current, low voltage (if not open circuited!) transformers and so need a very low impedance load to function accurately.
Why input resistance of voltage amplifier is infinity?
For the successful amplification of the input signal the opamp should have ideally infinite input impedance . It should act like a buffer amplifierBUFFER amplifier--------------------->1.input impedance infinity2.output impedance zerothe reason is thatAny signal source will have source impedancefor the signal not to get lost and dropped across source impedance we ideally insert infinite impedance in series with it which makes the whole drop across the infinite impedance but not across the sourcesimilarly at the output zero impedance is used where in no part of the signal should be left behind in the op amp as a drop
What is the impedence?
Impedance is the complex form of resistance. Impedance takes into account capacitance and inductance in a circuit as well. Impedance can be represented as resistance as a function of frequency.See link.AnswerImpedance is not a 'complex form of resistance'. It is the vector sum of a circuit's resistance and reactance. In electrical engineering, 'resistance' has a very specific meaning, and cannot be used to denote 'opposition'.
Why the current increases upto resenance frequency and decreases there after in a series LCR circuit?
At resonance, the L and C impedance cancels out, so the current can be calculated based on the resistance and applied voltage. Imagine increasing frequency of the supply from 0 Hz to very high. At low frequency, the impedance of the inductor is ~0 (defined as Zl = w*L*j), and the impedance of the capacitor is very large (defined as Zc = 1 / (w*C*j)). As you increase the frequency, the impedance of the capacitor will decrease, as the impedance of the inductor increases. At some point (the resonant frequency), these two will be equal, with opposite signs. After crossing the resonant frequency, the inductor impedance will continue growing larger than the capacitor impedance until the total impedance approaches infinite.
Why a coil of wire placaed in series circuit allows low frequency current but not high frequency current to pass?
The opposition to an alternating current offered by a coil, or inductor, is called impedance (symbol Z, measured in ohms) which, in turn, is made up of two components: resistance (symbol R) and inductive reactance (symbol XL). These three quantities are related as follows: Z2 = R2 + XL2.The resistance of an inductor is a fixed value which depends upon the length of the coil's wire, the cross-sectional area of the wire, and the resistivity of the material from which the wire is made.The inductive reactance of an inductor, on the other hand is directly proportional to the frequency of the supply. So, at high frequencies, an inductor's inductive reactance is very much higher than at low frequencies.So, at high frequencies, the impedance of the inductor is higher because its inductive reactance is higher.The current flowing through a coil is, by Ohm's Law: I = V / Z. So, at high frequencies, the inductor's impedance will be much higher than at low frequencies, which means that a very much smaller current will flow when the frequency is high compare to when the frequency is low.
Compared to bipolars FETs have-a high input impedance b low input impedance c same input impedance?
FET s have very high input impedance when compared with Bipolar transistors.
Why initial current is always zero in an inductor and if it is due to 100 percent opposition then current should always remain zero because just after opposition current is zero than again?
When initially closing a switch into any electrical device, the initial condition will be zero current. I think you are getting confused about impulse response. An impulse (such as would result from closing a switch) is essentially a very short, high frequency wave. Inductors' impedance is equivalent to the wave frequency (in radians)*2*PI*inductance (in Henrys). You can see if the applied waveform is a very high frequency, the inductor's response will be to highly limit current flow. A capacitor's impedance is equivalent to 1/(frequency*2*Pi*capacitance); the impulse response of a capacitor is a very high current spike due to a very low impedance.
What are the main differences between FETs and BJTs in terms of input impedance?
FET has very high input impedanceBJT has very low input impedance
How will be the outputs across the inductor and resistor if you keep the frequency of the input signal very low?
For a low frequency source, the voltage across the inductor tends to zero because its impedance is proportionnal to source frequency, whereas the voltage across the resistor tends to the voltage source value.
Why fault current can be extremely high?
Because the impedance to current flow is very low.
What are the properties of an op-amp?
Properties of an op-amp are as follows: 1.Very high open loop gain which remains constant over the frequency range in which the device is to be used. 2.Very high input impedance to minimize the current drawn by the circuit with little losses. 3.Very low output impedance 4. They are stable, i.e. not liable to burst into parasitic oscillation. 5. They are free from drift caused by ambient temperature changes.
What effect does transformer has a very low impedance on short circuit current?
the short ckt curent will be very high.
Why input impedance of any amplifier should very high?
To get all the audio voltage from a source to a target without loss you need voltage bridging, that is a relative low output impedance to a higher input impedance. Usualy the input impedance is at least ten times higher then the output impedance.An input impedance is called also a load impedance or an external impedance.An output impedance is called also a source impedance or an internal impedance.
Which characteristics of Op-Amp is responsible for virtual ground?
The main parameter responsible for virtual ground of an Op-Amp is Input Impedance . Generally , for an Op-Amp it is very high . So , we can conclude that the characteristics of an Op-Amp responsible for virtual ground is high input impedance .
Why you go for bootstrap circuit?
Bootstrapping is used to allow bias to be applied to the base of a transistor while maintaining a very high input impedance.
