- CURRENTGiven an appropriate external force, the movement of electrons is from negatively charged atoms to positively charged atoms. This flow of electrons is called current (I). The symbol “I” is used to represent current. The amount of current is the sum of the charges of the moving electrons past a given point. An electron has …
- ATOMSAn atom is the smallest particle of an element that retains the characteristics of that element. Each of the known 110 elements has atoms that are different from the atoms of all other elements. This gives each element a unique atomic structure. According to the classic Bohr model, an atom is visualized as having a …
- MATTER, ELEMENTS AND COMPOUNDSMatter is anything that occupies space and has weight. It may be found in any one of three states: solid, liquid, or gas. An element is the basic building block of nature. It is a substance that cannot be reduced to a simpler substance by chemical means. Examples of elements are gold, silver. The chemical …
- fixed and variable resistorsA Linear resistor is one whose resistance doesn’t vary with the flow of current through it. The current through it, will always be proportional to the voltage applied across it. Linear resistors are further classified as Fixed and Variable resistors. Variable resistors are those whose values can be varied manually, according to the requirement. A …
- resistor color codingA process called resistor color coding is used to determine the value of resistance for a resistor, just as shown in the below figure. A resistor is coated with four color bands where each color determines a particular value. The below table shows a list of values which each color indicates. The first two colored …
- what is inverting amplifierinverting amplifier is One of the more popular circuit configurations of the op-amp, because of its simplicity, shown in below Figure . The input signal to be amplified is connected to the inverting terminal, while the noninverting terminal is grounded. It will now be shown how it is possible to choose an (almost) arbitrary gain …
- operational amplifierAn operational amplifier is an integrated circuit, that is, a large collection ofindividual electric and electronic circuits integrated on a single silicon wafer. An operational amplifier—or op-amp—can perform a great number of operations, such as addition, filtering, and integration, which are all based on the properties of ideal amplifiers and of ideal circuit elements. The …
- ideal op amp characteristicsOne of the most important functions in electronic instrumentation is that of amplification (ideal op amp characteristics ).The need to amplify low-level electric signals arises frequently in a number of applications. Perhaps the most familiar use of amplifiers arises in converting the low-voltage signal from a cassette tape player, a radio receiver, or a compact …
- thevenin theoremone of the most important topics in the analysis of electric circuits is the concept of an equivalent circuit. thevenin theorem show that it is always possible to view even a very complicated circuit in terms of much simpler equivalent source and load circuits, and that the transformations leading to equivalent circuits are easily managed, …
- mesh current methodmesh currents method is circuit analysis method. In the mesh current method, a current flowing through a resistor in a specified direction defines the polarity of the voltage across the resistor, and that the sum of the voltages around a closed circuit must equal zero, by KVL. Once a convention is established regarding the direction …
- ohm’s law definitionWhen electric current flows through a metal wire or through other circuit elements, it encounters a certain amount of resistance, the magnitude of which depends on the electrical properties of the material. practically all circuit elements exhibit some resistance; as a consequence, current flowing through an element will cause energy to be dissipated in the …
- what is electric powerThe definition of voltage as work per unit charge lends itself very conveniently to the introduction of power. Recall that power is defined as the work done per unit time. Thus, the power P either generated or dissipated by a circuit element can be represented by the following relationship: The electric power generated by an …
- kirchhoff’s voltage lawThe principle underlying kirchhoff’s voltage law KVL is that no energy is lost or created in an electric circuit; in circuit terms, the sum of all voltages associated with sources must equal the sum of the load voltages, so that the net voltage around a closed circuit is zero. The principles of conservation of energy …
- potential differenceCharge moving in an electric circuit gives rise to a current, Naturally, it must take some work, or energy, for the charge to move between two points in a circuit, say, from point a to point b. The total work per unit charge associated with the motion of charge between two points is called voltage. …
- kirchhoff’s current lawKirchhoff’s laws govern the conservation of charge and energy in electrical circuits. Kirchhoff’s Laws The junction rule The closed loop rule At any node (junction) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node, or: The algebraic sum of currents …
- elementary chargeThe word electricity originated about 600 B.C.; it comes from elektron, which was the ancient Greek word for amber. The true nature of electricity was not understood until much later. the atomic structure of matter, consisting of a nucleus—neutrons and protons—surrounded by electrons. The fundamental electric quantity is charge, and the smallest amount of charge …
- electrical network elementsAn electrical network is a collection of elements through which current flows. The following definitions introduce some important elements of a network. Branch A branch is any portion of a circuit with two terminals connected to it. A branch may consist of one or more circuit elements Node A node is the junction of two …
- ideal current sourceAn ideal current source is a device that can generate a prescribed current independent of the circuit to which it is connected. To do so, it must be able to generate an arbitrary voltage across its terminals.
- Ideal Voltage SourcesAn ideal voltage sources are an electric device that generates a prescribed voltage at its terminals. The ability of an ideal voltage source to generate its output voltage is not affected by the current it must supply to the other circuit elements. Note that the output voltage of an ideal source can be a function …
- what is residual currentNo commentary on protective devices would be complete without reference to residual current devices. The IEE Regulations specify that, provided the required disconnection times can be met for circuits and all bonding is in place, fuses and/or CBs will provide the necessary protection against electric shock. RCDs are only required • when disconnection times cannot …
- earth fault loop impedancecircuit protection should operate in the event of a fault to earth. The speed of operation of the protective device is of extreme importance and will depend on the impedance of the earth fault loop path. • the circuit protective conductor (CPC)• the consumer’s earthling terminal and earthing conductor• the return path, either metallic or …
- what is earthing in electricityThe thin layer of material which covers our planet – rock, clay, chalk or whatever – is what we in the world of electricity refer to as earth. So, why do we need to connect anything to it? After all, it is not as if earth is a good conductor It might be wise at …
- electric shockThis is the passage of current through the body of such magnitude as to have significant harmful effects. below Figure illustrates the generally accepted effects of current passing through the human body. How, then, are we at risk of electric shock and how do we protect against it? 1 mA–2 mA Barely perceptible, no harmful …
- what is analog multimeterThe basic analog multimeter is commonly referred to as a VOM (volt-ohmmilliammeter). The VOM shown measures ac and dc volts from 250 mV full scale to 1000 V, dc from 50 μA full scale to 10 A, ohms up to 20 M, and decibels (dB) with a total of 29 ranges. The accuracy on dc …
- how to charge a batteryThe batteries used in most industrial situations (other than standby emergency use) are used in what is called cyclic operation. That is, the battery is either being charged or being used (discharged). In most such applications batteries are charged about 1500 to 2000 times during their lives. Incorrect charging for a few cycles will do …
- what is lead acid batteryTwo types of lead-acid batteries are manufactured for industrial applications. These are generally referred to as motive-power and stationary batteries. Typical applications for motive-power batteries include material-handling trucks, mine locomotives, mine tractors, mine shuttle cars, floor sweepers and scrubbers, heavy-duty personnel carriers, transport vehicles, golf carts, and lawnmowers. Typical applications for stationary batteries are switchgear …
- motor troubleshootingThe following troubleshooting flowcharts should provide logical, step-by-step methods for determining solutions to motor problems. They should be used as a guideline by qualified competent personnel. Troubleshooting ac Motors A. Motor won’t start or accelerates too slowly.B. Motor runs noisy.C. Motor overheats.D. Motor bearings run hot or noisy. Troubleshooting dc Motors E. Motor won’t start.F. …
- electric motor maintenanceMaintenance Plan. A specific maintenance plan that is carried out on a regular basis is a primary factor in preventing motor problems and failures. And, when problems do arise and system shutdown is inevitable, a logical, step-by-step method of troubleshooting can save time and money. At the very least, the motor manufacturer’s maintenance schedule should …
- induction motor workingTheory and Construction. Induction motors are common in most industrial applications. They all have primaries, or stator windings, connected to a power source, with a secondary winding, or rotor, which drives the mechanical load. The most common type of induction motor is the squirrel-cage motor, so named because its rotor construction entails bars of copper …
- ac generator working principleNo-load operation The basic operation of all these generator types can be explained using two simple rules, the first for magnetic circuits and the second for the voltage induced in a conductor when subjected to a varying magnetic field.
- the oscilloscopeThe most commonly used instrument in electronic and electrical engineering is the cathode ray oscilloscope or its digital counterpart, the digital storage osciuoscope. It is difficult to envisage design, development, testing or maintenance without the oscilloscope. The oscilloscope makes visible the waveforms in the circuits of interest and is therefore the means whereby the engineer …