AC Circuit

Cause of Skin Effect in AC Conductors

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The behavior of AC current is different than the behavior of DC current. When DC current flows through a conductor, it get uniformly distributed over the whole cross-section of the conductor but when AC current flows, it has a tendency to flow near the surface of the conductor. This behavior of AC current is popularly … Read more

Why Capacitor is Generator of Reactive Power while Inductor an Absorber? Understanding Reactive Power

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Consider an Inductive circuit and assume the instantaneous voltage be v = VmSinωt   Then the current will lag behind the voltage by some angle Ø and the instantaneous current will be as   i = ImSin(ωt-Ø)   Now to understand the concept of Reactive Power, we will calculate the instantaneous power. The instantaneous power … Read more

Why do Capacitor Block DC but Allows AC

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All of us know that a Capacitor do not allow DC current to pass through it but allows AC current. In this post we will discuss this kind of behavior of Capacitor.First we will consider DC supply connected to a parallel plate capacitor as shown in figure below. Let the capacitance be C. So as … Read more

Calculation of Reactive Power of a Capacitor

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This post gives is a quick derivation of the formula for calculating the steady state reactive power absorbed by a capacitor when excited by a sinusoidal voltage source. Given a capacitor with a capacitance value of C in Farads, excited by a voltage source V in volts, it will draw a current i amps into … Read more

Difference between Star and Delta Connection

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As we know that Star & Delta Connection only possible in 3 phase system, so in our domestic system it is not possible, because generally all house hold electrical equipment are designed with single phase supply. Difference between Star & Delta: Star Connected System: Star connection is used where we require Neutral terminal to obtain … Read more

Difference between Impedance and Admittance

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Impedance is the resistive parameter offered to the flow of current in a circuit. Whenever current flows or electrons move through a closed circuit, due to collisions of electrons, resistance is offered to the flow of current. In a DC circuit, impedance is nothing but resistance. But in an AC circuit, along with resistance, inductance … Read more

Why we Replace Voltage Source with Short Circuit and Current Sources with Open Circuits in Thevenin’s and Norton’s Theorem?

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We don’t really replace the voltage sources with shorts rather we make the voltage of the voltage sources zero volts.  An ideal voltage source has zero internal impedance by definition of being “ideal”, so if we reduce its voltage to zero, we are left with a zero impedance source, which is a short circuit.  An … Read more

Concept of Transient State and Steady State

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The terms Steady State or Transient State is defined not only for electrical systems, but for many other physical systems also. The transient response does not depend on the source i.e. forcing function, applied. It is purely natural response. Mostly transient response is associated to on/off events. Previously the circuit is switched off. Now it … Read more

Why Inductor is Short Circuited in DC?

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As we know that from, Faraday law that a varying current will induce voltage in a coil. When a current passes through a coil it will generate its own magnetic field and this field cuts the same coil producing an emf across it by self induction (L=Coefficient of self induction).     The current which … Read more