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Electron Articles
Page 18 of 19
Thevenin's Theorem and Thevenin Equivalent Circuit
Thevenin’s Theorem is used, where it is desired to determine the current through or voltage across any one circuit element without going through the complex method of solving a set of network equations.Statement of Thevenin’s TheoremAny two terminal bilateral linear dc circuit can be replaced by an equivalent circuit consisting of voltage source in series with a resistance, the voltage source being the open circuited voltage across the open circuited load terminals and the resistance being the internal resistance of the source network looking through the open circuited load terminals.Explanation of Thevenin’s TheoremStep 1 – Remove the load resistor (RL) ...
Read MoreSource Transformation with Solved Examples
A practical voltage source consists of an ideal voltage source in series with an internal resistance (for an ideal voltage source, this internal resistance being zero, so that the output voltage becomes independent of the load current) While a practical current source consists of an ideal current source in parallel with an internal resistance (for an ideal current source, this parallel resistance is infinity).The practical voltage and current sources are mutually transferable i.e. a practical voltage source can be converted into a practical current source and vice-versa.Voltage to Current Source TransformationConsider a practical voltage of V volts having a series ...
Read MoreSeries RLC Circuit: Analysis and Example Problems
Consider the circuit consisting of R, L and C connected in series across a supply voltage of V (RMS) volts. The resulting current I (RMS) is flowing in the circuit. Since the R, L and C are connected in series, thus current is same through all the three elements. For the convenience of the analysis, the current can be taken as reference phasor. Therefore, $$\mathrm{Voltage\:acorss\:\mathit{R}, \mathit{V}_{R}=\mathit{IR}}$$$$\mathrm{Voltage\:acorss\:\mathit{L}, \mathit{V}_{L}=\mathit{IX}_{L}}$$$$\mathrm{Voltage\:acorss\:\mathit{C}, \mathit{V}_{C}=\mathit{IX}_{c}}$$Where, XL = jωL = Inductive Reactince, Xc = 1/jωC = Capacitive reactance. VR is in phase with I. VL is leading the current I by 90°. VC is lagging the I by 90°.The total voltage ...
Read MoreResistors in Series
The resistors are said to be connected in series, when they are joined end to end so that there is only one path for the current to flow.ExplanationLet the three pure resistors R1, R2 and R3 be connected in series against a DC voltage source V as shown in the circuit.Referring the circuit it can be written that$$\mathrm{\mathit{V}\:=\:\mathit{V}_{1}+\mathit{V}_{2}+\mathit{V}_{3}\:\:\:\:…(1)}$$Where V1, V2 and V3 being the voltage drops against individual resistors.Assuming I to be the total current in the circuit and R being the equivalent resistance of all the series resistors. Hence, the equation (1) can be written as$$\mathrm{\mathit{IR}=\mathit{IR}_{1}+\mathit{IR}_{2}+\mathit{IR}_{3}}$$$$\mathrm{\Rightarrow\:\mathit{R}=\mathit{R}_{1}+\mathit{R}_{2}+\mathit{R}_{3}\:\:\:\:…(2)}$$Thus, the equation (2) ...
Read MoreResistors in Parallel
When one end of each resistor is joined to a common point and the other end of each resistor is joined to another common point so that there are as many paths for current flow as the number of resistors, it is called as a parallel circuit.The below circuit shows the connection of three resistors in parallel across a DC voltage source V. Let the circuit current be 𝐼 while the branch currents I1, I2 and I3 respectively. The voltage drop in each branch being same, so by Ohm’s law, we can write, $$\mathrm{\mathit{V}=\mathit{I}_{1}\mathit{R}_{1}=\mathit{I}_{2}\mathit{R}_{2}=\mathit{I}_{3}\mathit{R}_{3}}$$Also, by referring the circuit, $$\mathrm{\mathit{I}=\mathit{I}_{1}+\mathit{I}_{2}+\mathit{I}_{3}}$$$$\mathrm{\Rightarrow\frac{\mathit{V}}{\mathit{R}_{p}}=\frac{\mathit{V}}{\mathit{R}_{1}}+\frac{\mathit{V}}{\mathit{R}_{2}}+\frac{\mathit{V}}{\mathit{R}_{3}}}$$Where, RP ...
Read MoreMagnetism, Electromagnetism & Magnetic Materials
MagnetismIn the ancient times, people believed that the invisible forces of magnetism was purely a magical quantity. However, with the increasing scientific knowledge over the passing centuries, magnetism assumed a larger and larger role. Today the magnetism has attained a place of pride in electrical engineering. Without the magnetism, it is impossible to operated electrical devices like generators, motors, transformers, TV, radio, telephone etc. Therefore, electrical engineering is much dependent on magnetism.Magnetic polesA magnet has two poles viz. North Pole and South Pole. In order to determine the polarity of a magnet, suspend it at its centre, then the magnet ...
Read MoreLoaded and Unloaded Voltage Dividers
A voltage divider or potential divider is a series circuit that is used to provide more than one reduced voltages from a single source of voltage.Consider a circuit of voltage divider as shown below, in which two reduced voltages V1 and V2 are obtained from a single input voltage source of V volts. Since no load is connected to circuit, it is called unloaded voltage divider.Refer the circuit of unloaded voltage divider, $$\mathrm{Circuit\:Current, I= \frac{V}{R_{1}+{R_{2}}}=\frac{V}{R_{eq}}}\:\:\:… (1)$$ Where, Req=R1 + R2= Total resistance of voltage dividerTherefore, $$\mathrm{V_{1}=IR_{1}=\frac{V}{R_{eq}}×R_{1}=V\frac{R_{1}}{R_{eq}}}\:\:\:… (2)$$$$\mathrm{V_{2}=IR_{2}=\frac{V}{R_{eq}}×R_{2}=V\frac{R_{2}}{R_{eq}}}\:\:\:… (3)$$Hence, equation (2) and (3) shows that, the voltage drop ...
Read MoreInductors in AC Circuits
Consider the circuit containing a pure inductive coil of inductance L Henry. When an alternating voltage V (RMS) is applied across the coil, an alternating current I (RMS) will flow through the circuit. Due to this alternating current, a back emf (e) is induced in the coil due to inductance of it. This back emf at every instant opposes the any change in current through the coil.Let the applied alternating voltage is$$\mathrm{u=V_{m}sin\:\omega t}\:\:\:… (1)$$The back emf (e) induced in the inductor coil is given by, $$\mathrm{e=L \frac{di}{dt}}\:\:\:… (2)$$Since, there is no ohmic drop, thus the applied voltage has to overcome ...
Read MoreDifference between Diamagnetism, Paramagnetism, and Ferromagnetism
In order to differentiate the diamagnetism, paramagnetism, and ferromagnetism, first we need to understand, the concept of magnetism and diamagnetism, paramagnetism and ferromagnetism individually.Concept of MagnetismElectrons exhibit two types of angular momenta − Orbital Angular Momenta and Spin Angular Momenta . The orbital angular momentum is a property of electrons when they are in atoms while the spin angular momentum is an intrinsic property of electrons. With these angular momenta, a magnetic moment is associated. That magnetic moment is a property which causes the electrons to experience a force, when they are placed in a magnetic field.The orbital magnetic moment ...
Read MoreCharacteristics of Network and Electric Circuit
Electric NetworkAn electrical network is an interconnection of electrical components (like sources, resistors, inductors, capacitors, diodes, transistors etc.). An electrical network need not contain a closed path for the flow of electric current. Some examples of the network are shown in the figure given below.Characteristics of Electric NetworkAn electric network possesses the following characteristics −It is an interconnection of electrical components.Electric network need not provide a return path for the current.It may or may not contain active electrical components.It may be consist of, passive elements, active elements or both active and passive elements.Examples of electric network are − Resistive network, ...
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