Bolkowski Stanisław, Brociek Wiesław, Rawa Henryk: Teoria obwodów elektrycznych – Zadania, Wydanie VI – zmienione i uzupełnione, , WNT, ISBN. : Teoria obwodow elektrycznych () by Stanislaw Bolkowski and a great selection of similar New, Used and Collectible Books. Stanisław Bolkowski is the author of Teoria obwodów elektrycznych ( avg rating, 2 ratings, 0 reviews).
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Base units are defined units, i. Engineering Notation In engineering notation, prefixes are used bolokwski represent certain powers of The of significant digits as a result of multiplication, division, addition or subtraction is the same as the of significant digits in the number with the least number of significant digits.
Cu atom has 29 electrons, 29 protons, and 35 neutrons. Si, which is important because of its use in transistors and other electronic devices, has 14 electrons, 14 protons, and 14 neutrons. Cu has all three inner shells completely filled but its outer shell N obwodo only 1 electron. Valence Shells No element can have more than 8 valence electrons.
When a valence shell has 8 electrons, it is filled. Free Electrons The force of attraction keeps the electrons in orbit. These escaped electrons wander from atom to atom and are called free electrons. If a body has an excess of electrons, it is negatively charged; if there is a deficiency, it is positively charged. Commonly encountered in daily live as static electricity. Later, 7 x electrons are removed.
Compute the force between them. Is the force repulsive or attractive? Several thousand volts could be developed in static electricity and several hundred million volts could be created in a thunderstorm.
A battery dry cell is a common example of dc direct current voltage sources.
It is based on the chemical reaction inside the cell. Work is required to move positive and negative charges apart. The voltage between two points is 10 V. How much energy is required to move 3 x electrons from one point to the other? A pracitcal way to measure voltage is to use a voltmeter.
In a metal,such as Cu, there are large numbers of free electrons moving randomly throughout it but the net movement in any given direction is zero. If a battery is connected as shown above, electrons are attracted to the positive pole, passing through the wire and the lamp. The movement of charge is called an electric current. How many electrons pass through a circuit in 10 ms if the dc current is 2 A? Current is measured with an ammeter.
Conventional current flow will be used throughout this course. AC or alternating current is current that changes direction cyclically, i. The voltage of a battery, its service life, and other characteristics depend on the material from which it is made. Alkaline battery is one of the most widely used, general purpose primary cell available. Cell voltage is 1. Carbon-Zinc battery dry cell was the most popular. Sizes and voltage are the same as alkaline. Lithium battery features small size, low cost, and long shelf life.
Cell voltages are available from V. NiCads are the most popular rechargeable batteries. They have long service lives, operate over wide temperature ranges, and have many styles and sizes.
Lead acid commonly found in automotive batteries. Cell voltage is 2 V. Battery Capacity is specified in Ah. It is affected by discharge rates, operating schedules, temperature, and other factors. Life is shortened at low as well as at high temperatures. Cells are often put in parallel or in series to increase their current or voltage respectively. Other dc voltage sources Electronic power supplies rectify ac to dc. Their voltage may be fixed for equipment, TV, etc.
DC generators convert mechanical energy to electrical energy by rotating a coil of wire through a magnetic field.
Fuses use a metallic element that melts when current exceeds a preset value. They are available as fast-blow and slow-blow types. Slow-blow fuses do not bolkowsko on small, momentary overloads. An ohmmeter can be used to check whether the fuse has owbodow. Circuit breakers depend on the magnetic field produced by the excessive current to operate a mechanism that trips open a switch. After the fault or overload condition has been cleared, the breaker can be reset and used again.
Their operation is slower than that of a fuse.
Elektronika i Elektrotechnika
The electrons collide with atoms and other electrons and these collisions give feoria to resistance to the current flow. R depends on the type of material, the length of the conductor, the x-sectional area and temperature. Determine the resistance of m of AWG 20 solid copper wire. AWG is still widely used in the U. Most applications do not use solid conductor sizes beyond AWG 10 because they are difficult to bend and easily damaged by mechanical flexing.
Teoria obwodów elektrycznych – Stanisław Bolkowski – Google Books
Large-diameter cables are nearly always ogwodow rather than solid. Since not all conductors have circular x-sections, it is occasionally necessary to convert areas in square mil sq. Temperature Effectsb As T increases, more electrons will escape their orbits, causing additional collisions within the conductor.
For most materials, R increases almost linearly with T. Semiconductor materials, however, have -ve a. A copper wire has a resistance of 10 W at 20o C. Calculate its resistance at o C and o C. Fixed resistors have essentially constant resistance values. Carbon composition resistors consist of a carbon core mixed with an insulating filler. The ratio of carbon bbolkowski filler determines the resistance. The entire resistor is encapsulated with an insulated coating.
Where precision is important, film resistors are usually employed. If close tolerances are required, films of alloys such as NiCr, constantum, or manganin, are used. Wire-wound resistors made of a metal alloy wound around a hollow porcelain core and covered with a thin layer of porcelain are used for dissipating large quantity of heat. IC resistor packages containing many individual resistors are used to conserve space on pcb.
Variable resistors consist of 3 terminals, two of which are fixed to the ends of the resistive material. A wiper enables the resistance between the central terminal and either terminal to change.
Potentiometers are used to adjust the amount of potential provided teogia a circuit. Rheostats are used to adjust the amount of current within a circuit. Their connection is similar to that of potentiometers except one of the end terminals is not connected. Smaller resistors use coloured bands.
Determine the resistance of a resistor having the colour codes: What are the possible maximum and minimum values of this resistor? Resistance is measured with an ohmmeter which is generally part of a multimeter.
Bolkowski, Stanisław (1930- ).
Remember to isolate the resistor and switch off all power supplies from the circuit when measuring R. Ensure the ohmmeter is on the correct range to provide the most accurate reading.
If the resistor is open, an analog ohmmeter will read infinity while a digital one will read OL or Turn off the ohmmeter when finished to conserve battery. If a device has a nonlinear V-I characteristic, it is referred to as a nonohmic device.
Obwodoow and varistors are such devices. When the voltage across a varistor exceeds owodow rated value, its resistance suddenly becomes very small. Thus varistors are used as overvoltage protection devices. The resistance of thermistors drops with temperature. They are suitable for use in circuits to control current and to measure or control temperature. Doubling the voltage, E, doubles the current, I.
Doubling R halves I. What is the value of R in the circuit teoriaa A 20 V source is connected across a W resistor. Determine the current through the resistor.
Obwodoow voltages are sometimes referred to as IR drops. If the actual current is in the direction of its reference arrow, it will have a positive value, while if it is opposite to its reference arrow, it will have a negative value.