What is a pure inductive circuit, and what is the response of. This is the multiples choice questions part 1 of the series in electrical circuit as one of the electronics engineering topic. It helps illustrate a very useful characteristic of inductive circuitsthe current through the inductor always lags the voltage across the inductor. In this example, the current to the load would be 2 amps, rms. So whenever a sinusoidal voltage is applied to an inductive coil, the back emf opposes the rise and fall of the current flowing through the coil and in a purely. The power factor of a resistive circuit is always zero b. Lessons in electric circuits volume ii ac chapter 11. Chapter 2 inductors, capacitors and alternating current.
Why power in pure inductive and pure capacitive circuit is. In an inductive circuit the reactance is given by jwl. Jul 28, 2015 in a purely resistive circuit, current and voltage are in phase with one another. In preparation for the ece board exam make sure to expose yourself and familiarize in each and every questions compiled here taken from various sources including but not limited to past board exam questions in electronics engineering field, electronics books, journals.
Figure below current lags voltage in a series lr circuit. Purely resistive ac circuits effect of resistance in dc and ac circuits purely resistance circuits consist of electrical devices, which contain no inductance or capacitance. So lets back to the basic to clear the basic and important concepts of electrical engineering. In a purely resistive circuit, current and voltage are in phase with one another. Purely inductive circuit mathematical proof for current. Power factor of electric bulb is a zero b lagging c leading d unity ans. At what angular frequency w is the maximum current 2. A pure inductor is connected across a 10 v, 200 hz supply, and the current flowing. Reactance is symbolized by the capital letter x and is measured in ohms just like resistance r. The expression for inductive reactance and the relationship between current and voltage in an inductive circuit are derived from this equation which assumes that the circuit under consideration is purely inductive.
Pure resistive ac circuit the circuit containing only a pure resistance of r ohms in the ac circuit is known as pure resistive ac circuit. The amplitude of the current will decrease and the voltage will remain unchanged. As with the purely inductive circuit, the current wave lags behind the voltage wave of the source, although this time the lag is not as great. While our example above represents a simple nonpure ac inductance, if two or more inductive coils are connected together in series or a single coil is connected in series with many non inductive resistances, then the total resistance for the resistive elements would be equal to. Why power in pure inductive and pure capacitive circuit is zero. The current lags the voltage in a capacitive circuit.
Ac inductance and inductive reactance in an ac circuit. Series rlc resonant circuits electronics tutorials. Ac inductive circuits september 15, 2015 by administrator leave a comment an inductor is usually a coil of wire that sets up an alternating magnetic field around it when an alternating current flows through it. Given below is the schematic representation of the purely inductive ac circuit. Your question infers sine function but doesnt say thats what it is. In a purely inductive circuit, current lags the voltage by 90 current being the purple waveform. How does the current flow in purely inductive circuit. Here, the power triangle would look like a horizontal line, because the opposite reactive power side would have zero length. If we increase the driving frequency in a circuit with a. This condition of resonance unity power factor or purely resistive impedance may occur in two ways. Series resistorinductor circuits workforce libretexts. Devices such as resistors, lamps incandescent and heating elements have negligible inductance or capacitance and for practical purposes can be considered to be purely resistive. Because inductors are larger, heavier, and more expensive than capacitors, they have fewer applications than capacitors.
In pure inductive circuit or capacitive circuit where voltage is leading by 90 from current and current is leading 90 from voltage respectively. Inductance opposes change in current due to the back emf effect. This will increase the amplitude of the current and the voltage will remain unchanged. However, inductors have the advantage of providing a reactive effect while still completing a dc circuit path. The current leads 90 electrical in respect of the applied voltage in a purely capacitive circuit. In this type of circuit, the current lags behind the voltage by an angle of 90 degrees. But since reactance is already expressed in the form of ohms in a purely reactive circuit ohms laws applies normally for a purely. Find the inductive reactance and rms current in the.
Inductive reactance can be calculated using this formula. Why power is zero 0, in pure inductive, pure capacitive or. So if we put cos 90 0, then the overall power of the circuit will be zero i. Apparent power the product of the voltage and current in a circuit, calculated without considering the phase shift that may be present between the voltages and current in a circuit. Jan 19, 2016 purely resistive ac circuits effect of resistance in dc and ac circuits purely resistance circuits consist of electrical devices, which contain no inductance or capacitance. The alternating current and voltage both move forward as well as backwards in both the direction of the circuit. This causes the current to reach its peak value some time after the voltage. In dc circuits the current eventually settles to a. Eece 251, set 4 sm 32 eece 251, set 4 source free or zeroinput firstorder circuit recall that in general if there is only one equivalent inductor or capacitor in the circuit one can model the circuit seen by the inductor or capacitor by its thevenin equivalent circuit. In a purely inductive circuit, the rms voltage is 129 v. Current i lags applied voltage e in a purely inductive circuit by 90 phase angle.
This ratio of voltage to current is the opposition offered by the inductive circuit to the current flow. Voltage and current phase relationships in an inductive circuit. Ac inductor circuits reactance and impedance inductive. For the purely resistive circuit, the power factor is 1 perfect, because the reactive power equals zero. Purely resistive inductive capacitive circuit your. Loads consisting of any heating element are classified as resistive loads. In a purely inductive circuit, voltage and current are 90 degrees out of phase with each other. Which one of the following circuits is a firstorder circuit. Physics mcqs for competitive exams part 3 translation in.
Nov 17, 20 in a purely inductive ac circuit, as shown in figure 33. The current flowing in a purely inductive ac circuit lags behind the applied voltage by 90 degrees. The phasor diagram of a pure inductive ac circuit is given below. I always think that the current in an inductive circuit is only because of the resistance associated with the coil. From the above derivation, the maximum current equation is given as. We are now here to discuss how in a purely capacitive circuit, current leads the. Applications of inductive circuits inductive circuits are widely used in electronics. May 03, 2019 this is the multiples choice questions part 1 of the series in electrical circuit as one of the electronics engineering topic.
The current in the purely inductive circuit will be doubled if the frequency of the circuit is halved. In a purely inductive circuit the voltage and current waveforms are not in phase. In the inductive circuit, however, the current reaches zero 90. The circuit which contains only inductance l and not any other quantities like resistance and capacitance in the circuit is called a pure inductive circuit. Inductive reactance is the opposition that an inductor offers to alternating current due to its phaseshifted storage and release of energy in its magnetic field. While our example above represents a simple nonpure ac inductance, if two or more inductive coils are connected together in series or a single coil is connected in series with many noninductive resistances, then the total resistance for the resistive elements would be equal to. Jan 02, 2019 the current lags 90 electrical in respect of the applied voltage in a purely inductive circuit. From equation 1 and 2 we observe that in a pure inductive circuit, the current lags behind the voltage by 90 hence the voltage and current waveforms and. Quiz 1 purely resistive circuit free class notes online. We are now here to discuss how in a purely capacitive circuit, current leads the voltage by 90 current being the purple waveform. Assume a pure inductive circuit and answer the following. Figure below ac source drives a purely resistive load. For this introduction to alternating current ac circuits analysis quiz, students are to mathematically solve the following ac series circuit problem. These include incandescent lights, toasters, ovens, space heaters and coffee makers.
If the circuit contains both in ductance and resistance, the phase angle will be. Read about ac inductor circuits reactance and impedance inductive in our free electronics textbook. Chapter 2 inductors, capacitors and alternating current circuits free download as powerpoint presentation. Chapter 12 alternatingcurrent circuits mit opencourseware. The power dissipated at the load would be 240 watts. Power in resistive and reactive ac circuits power factor. As we shall see below, a purely inductive circuit corresponds to infinite capacitance. Aug 31, 2009 this will increase the amplitude of the current and the voltage will remain unchanged. The presence of inductance and capacitance does not exist in a purely resistive circuit.
If the frequency of a pure inductive circuit is halved, then. Electronic circuit design using capacitors and inductors. Aug 21, 2017 how we can mathematically prove that in a purely inductive circuit current lags behind voltage by a phase angle of. The circuit containing pure inductance is shown below.
True power in an inductive circuit always equals the apparent power c. Note that the cur rent is zero when the voltage is zero and the current is maximum when the voltage is max imum in the resistive circuit. Applying the modified kirchhoffs rule for inductors, the circuit equation reads c. Jun 30, 2009 in a purely inductive circuit, the rms voltage is 129 v.
Inductive reactance varies directly with the source frequency d. The phase relationships in a resistive circuit and a purely inductive circuit are shown in the illustrations on page 92. The current does not lag as well as not lead in respect to the applied voltage in a purely resistive circuit. Sep 15, 2015 ac inductive circuits september 15, 2015 by administrator leave a comment an inductor is usually a coil of wire that sets up an alternating magnetic field around it when an alternating current flows through it. Solved in a purely inductive circuit, the rms voltage is.
Inductance is the property of an inductor that opposes the change in current. Consider a circuit for a singlephase ac power system, where a 120 volt, 60 hz ac voltage source is delivering power to a resistive load. Its true that in a purely reactive circuit, there is no power being continually dissipated. The phasor diagram shows the applied voltage e vector leading above the current i vector by the amount of the phase angle differential due to the relationship between voltage and current in an inductive circuit. First you have to define voltage as some math function. Such a circuit is called is called series rlc resonant circuit.
In a purely resistive circuit whole of the applied voltage is utilized in overcoming the ohmic resistance of the circuit. A purely resistive circuit is a circuit which has inductance so small that at normal frequency its reactance is negligible as compared to its resistance. In a purely resistive circuit, current and voltage are in sync or in phase with one another. A load that draws current in a sinusoidal waxingandwaning pattern in concert with a sinusoidal variation in voltage that is, the maximum, minimum and zero points of the voltage and. The total opposition of any combination of resistance, inductive reactance, and capacitive reactance offered to the flow of ac. In a purely inductive circuit a actual power is zero b reactive power is zero c apparent power is zero d none of above is zero ans. Consider a purely resistive circuit with a resistor connected to an ac generator. These types of questions are asked in electrical or electronics engineering interviews. Under resonance, the circuit has unity one power factor. How does voltage lead current in an inductive circuit. For the purely inductive circuit, the power factor is zero, because true power equals zero. Get answer in a purely inductive ac circuit, as shown in.
Theory of power in ac circuits i, instantaneous and average power. Why power is zero 0 in pure inductive, pure capacitive or a circuit in which current and voltage are 90 out of phase. Going back to first principles, a circuit is purely inductive if the instantaneous supply voltage causes a directly proportional rate of change of the instantaneous current consumed. A lamp is connected in a series with a capacitor and an ac source, what happens if the capacity of the capacitor is. A purely inductive ac circuit in a purely inductive ac circuit see active fig. Hence we conclude that in a purely inductive circuit the current lags behind the applied voltage by an angle. Inductors compete with capacitors for filtering and phaseshift applications. In a purely inductive ac circuit, as shown in figure 33.
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