This shows that a pure resistance within an ac circuit produces a relationship between its voltage and current phasors in exactly the same way as it would relate. In fact, the i or rms current is the equivalent dc current that would produce the same average power loss as the alternating current. As we saw with work, energy changed only when a portion of the force was in the direction of the displacement. Alternating current applications a transformer can only operate with alternating current to step up or step down an ac voltage. When placed in the vicinity of a currentcarrying conductor, the needle of a compass becomes aligned at what angle to the conductor. Effective value or rms value of ac it is defined as the value of ac over a complete cycle which would generate same amount of heat in a given resistors that is generated by steady current in the same resistor and in. Each cycle of alternating current or voltage consists of two half cycles, during one of which the current or voltage. A degree is a unit of measurement in degree its designation is or deg, a turn of a ray by the 60 part of the one complete revolution.
Then we will step through each of these topics in detail. Basic concepts of alternating current ced engineering. A current or voltage is called alternating if it reverses periodically in direction, and its magnitude undergoes a definite cycle of changes in definite intervals of time. In an alternating current circuit, voltage periodically reverses itself. Alternating current ac introduction flight mechanic. Introduction to basic notions on electric power 5 electric current conductor lines of force fig. Such current is used in your household to run the air conditioner, refrigerator, washing machine, and other electric appliances. The topics in this book are arranged to build readers knowledge, progressing from basic principles such as the differences between peak. The current in the circuit is impeded by the back emf of the inductor coil. Dc is the kind of electricity made by a battery with definite positive and negative terminals, or the kind of charge generated by rubbing certain types of materials. In an alternatingcurrent circuit, voltage periodically reverses itself. In more restricted sense, alternating current is a periodically varying current, the average value of which, over a period, is zero. The crest factor is the ratio of the peak value of an alternating current or voltage to the root mean square of the waveform.
This conversion of ac into dc is accomplished through the use of a commutator. These video classes have been designed to suit the curriculum of cbse class 12 students. D full solution available in student solutions manualstudy guide. Figure 1 shows the plot of alternating voltage and alternating current as a function of time in a circuit that has only a resistor and a source of alternating current an ac generator. Ac power refers to the 60 hz alternating voltage available from a common outlet. Basic concepts of alternating current cedengineering. Download cbse class 12th revision notes for chapter 7 alternating current in pdf format for free. In this current, the charged particles move from zero to maximum value in a direction and fall to zero and goes for another cycle in the opposite. Where vpeak is the maximum amplitude of the waveform. Chapter ac alternating current circuits page 3 exploration ac. Either as a voltage switching polarity or as a current switching direction back and forth, this kind of electricity is known as alternating current ac. Important questions for cbse class 12 physics introduction to. Most students of electricity begin their study with what is known as direct current dc, which is electricity flowing in a constant direction, andor possessing a voltage with constant polarity.
The lefthand rule for a conductor is used for what purpose q9. In fact, ac and dc motor designs are very similar to their generator counterparts identical for the sake of this tutorial, the ac motor being dependent upon the. Alternating current is when current flows in one direction for a set time, then changes direction, then changes back, and so on in a repeating cycle. What is the direction of the magnetic field around a vertical conductor when a the current flows upward and b the current flows downward. Fundamentals of alternating current 3 figure 121 sinusoidal wave values.
Alternating current circuits and electromagnetic waves. Rather than oscillating back and forth, dc provides a constant voltage or current. Alternating current ac it is the current which varies in both magnitude as well as direction alternatively and periodically. The solution of alternating current circuits chapter2 instantaneous current, voltage, and power a frequency. This device is a special type of electrical generator designed to produce alternating current. One of the key properties of an ac waveform, asides frequency and period, is the amplitude which represents the maximum value of an alternating waveform or as better known, the peak value peak as the word denotes, is the highest attained value by an alternating currents or voltage waveform during an half cycle of the waveform measured from the. Direct current dc is used on systems that must be compatible with battery. Alternating current refers to currents and voltages which are harmonic functions. Use of a device called a rectifier that converts ac to dc. With this method, the voltage forces the electrons to flow continuously in one direction through a closed circuit. Download revision notes for alternating current class 12 notes and score high in exams. Basically, what is alternating in alternating current is the polarity of the voltage source, which causes the current to flow in one direction, and then reverse, and flow in the opposite direction.
Alternating current ac electrical systems are found on most multiengine, high performance turbine powered aircraft and transport category aircraft. Alternating series test we have the following test for such alternating series. The voltage and the current are out of phase by 90 o. However, it is possible to convert the alternating current that is induced into the armature into a form of direct current. For simplicity, we sill assume that phase is 0 for the rest of this tutorial. Jan 24, 2018 ac circuits as the name alternating current implies are simply circuits powered by an alternating source, either voltage or current. Alternating current describes the flow of charge that changes direction periodically. Pn 10 x 360 120 120 30 hz b here, 120 120f for f 25 hz n 500 rpm f 60 n 1200 rpm 2. This type of voltage is called direct current dc voltage. Capacitance is important with the changing electric. In electrical circuits energy is dissipated only if a portion of the voltage is in phase with the current. Electric charge in alternating current ac, on the other hand, changes direction periodically. The direction of the lines of force is given by the law of the screwdriver.
Each cycle of alternating current or voltage consists of two half cycles, during one of which the current or voltage acts in one direction. It can be represented as, the currents and voltages in a. Class 12 physics notes chapter 7 alternating current. In this manner, as more turns are added to the coil, the same current produces larger and larger magnetic. Important questions for cbse class 12 physics introduction. Figure 1 current and voltage from an ac source through a simple resistor. Generating ac ac can be produced using a device called an alternator. Any voltage or current may be represented as a sum of harmonic voltages or currents and the. C is the current that changes in magnitude direction continuously with respect to time. Alternating current fundamentals, 8e, an industrial standard for over thirty years, has been updated to provide readers with the most current information available on the essentials of alternating current. When the voltage reverses, so does the direction of the current flow. Basic electrical theory overview of ac motors, transformers and measuring instruments instructor.
Sep, 2016 number of times this current changes its direction in one second can be defined as the frequency of the alternating current. At a particular instant in time, the current in the circuit. In fact, ac and dc motor designs are very similar to their generator counterparts identical for the sake of this tutorial, the ac motor being dependent upon the reversing magnetic field produced by alternating current through its stationary coils of wire to rotate the rotating magnet around on its shaft, and the dc motor being dependent on. At a particular instant in time, the current in the circuit is 2. In this video tutorial, we will understand the basic properties of alternating current ac and cover topics such as ac generator, current through ac generator, ac circuits, power factor, wattless current, and transformers. V, i maximum potential difference current voltage current amplitude. Alternating current full basics in hindi beee first year. The effective resistance is called the inductive reactance x l defined by x l 2.
With this method, voltage forces electrons to flow first in one. Electric charge in alternating current ac, on the other hand, changes direction. To explain the concept of alternating current, we begin by discussing the. Dc is the kind of electricity made by a battery with definite positive and negative terminals, or the kind of. In the most common form of alternating current, used in most power distribution systems throughout the world, the voltage reverses itself either 50 or 60 times per second, depending on the country. Upon completion of this chapter you will be able to. Alternating current class 12 notes physics mycbseguide. This portable document format \pdf\ file contains bookmarks, thumbnails, and hyperlinks to help you navigate through the document. Mar 05, 2019 class 12 physics notes chapter 7 alternating current. Alternating current fundamentals, 8e, an industrial standard for over thirty years, has been updated to provide your students with the most current information available on the essentials of alternating current. The handbook includes information on alternating current ac and direct current dc theory, circuits, motors, and.
Dec 01, 2015 alternating current ac it is the current which varies in both magnitude as well as direction alternatively and periodically. The latter unit is used in recognition of heinrich hertz, a german physicist who proved the existence and transmission of electric oscillations. Ac circuit analysis has a more general motivation and application. Learn the fundamentals of alternating current ac and its advantages over dc voltage. An alternating current or voltage, is one in which the value of either the voltage or the current varies about a particular mean value and reverses direction periodically. Notes on alternating current class 12 page 01 alternating current a. Both ac and dc describe types of current flow in a circuit. Why, alternating current and direct current, of course.
Ii alternating current ac with direct current covered and understood it is now time to delve into the world of alternating current. Ac fundamentals impedance power factor power series. An alternating current or voltage is the one which changes periodically both in cycle magnitude and direction. This designation indicates ac current goes through exactly 60 complete cycles of current alternations in each second. Pdf file contains bookmarks, thumbnails, and hyperlinks to help you navigate through the document.
Ac is the same type of electricity used in industry and to power our homes. As a result, the voltage level also reverses along with the current. State the differences between ac and dc voltage and current. Chapter 31 alternating current phasors and alternating currents resistance and reactance magneticfield energy the lrc series circuit power in alternatingcurrent circuits resonance in alternatingcurrent circuits transformers.
These video classes have been designed to suit the curriculum of. In particular, if a coil rotates in the presence of a magnetic field, the induced emf varies sinusoidally with time and leads to an alternating current ac, and provides a source of ac. A transformer is an example of inductance in ac circuits where the changing magnetic flux of a varying current produces an induced voltage. Thats why the main difference you will see between dc and ac circuit diagrams, is that in the ac circuit diagrams, there will be no indication of. An alternating currentac is a current that varies sinusoidally with time. Alternating current archives electronics tutorials. Ac is used to deliver power to houses, office buildings, etc. In direct current dc, the electric charge current only flows in one direction. Number of times this current changes its direction in one second can be defined as the frequency of the alternating current. An ac generator equipped with a device called a commutator can produce direct current. Direct current is a bit easier to understand than alternating current.
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