File Name: concept of voltage current resistance power and energy .zip
In electronics and electromagnetism , the electrical resistance of an object is a measure of its opposition to the flow of electric current.
- Electric Circuits 10th Pdf
- Current, Resistance, Voltage, and Power
- Voltage drop
- Voltage, Current, Resistance, and Ohm's Law
Electric Circuits 10th Pdf
Power is associated by many people with electricity. Knowing that power is the rate of energy use or energy conversion, what is the expression for electric power? Power transmission lines might come to mind. We also think of lightbulbs in terms of their power ratings in watts. Let us compare a W bulb with a W bulb. See Figure 1 a. Since both operate on the same voltage, the W bulb must draw more current to have a greater power rating.
If we increase voltage, we also increase power. For example, when a W bulb that is designed to operate on V is connected to V, it briefly glows very brightly and then burns out. Precisely how are voltage, current, and resistance related to electric power? Figure 1. Which draws more current?
Which uses the most energy? Can you tell from the color that the W filament is cooler? Is the brighter bulb a different color and if so why? Electric energy depends on both the voltage involved and the charge moved. Power is the rate at which energy is moved, and so electric power is. Electric power P is simply the product of current times voltage. Power has familiar units of watts. Since the SI unit for potential energy PE is the joule, power has units of joules per second, or watts.
For example, cars often have one or more auxiliary power outlets with which you can charge a cell phone or other electronic devices. Three expressions for electric power are listed together here for convenience:. Note that the first equation is always valid, whereas the other two can be used only for resistors. In a simple circuit, with one voltage source and a single resistor, the power supplied by the voltage source and that dissipated by the resistor are identical. In more complicated circuits, P can be the power dissipated by a single device and not the total power in the circuit.
Different insights can be gained from the three different expressions for electric power. Thus, when the voltage is doubled to a W bulb, its power nearly quadruples to about W, burning it out. Then find the power dissipated by the car headlight in these examples, both when it is hot and when it is cold.
The 30 W dissipated by the hot headlight is typical. But the W when cold is surprisingly higher. The current when the bulb is cold can be found several different ways. The cold current is remarkably higher than the steady-state value of 2.
Most fuses and circuit breakers used to limit the current in a circuit are designed to tolerate very high currents briefly as a device comes on.
The more electric appliances you use and the longer they are left on, the higher your electric bill. This familiar fact is based on the relationship between energy and power. You pay for the energy used. For example, the more lightbulbs burning, the greater P used; the longer they are on, the greater t is. It is easy to estimate the cost of operating electric appliances if you have some idea of their power consumption rate in watts or kilowatts, the time they are on in hours, and the cost per kilowatt-hour for your electric utility.
Kilowatt-hours, like all other specialized energy units such as food calories, can be converted to joules. The electrical energy E used can be reduced either by reducing the time of use or by reducing the power consumption of that appliance or fixture. This will not only reduce the cost, but it will also result in a reduced impact on the environment. Improvements to lighting are some of the fastest ways to reduce the electrical energy used in a home or business.
Fluorescent lights are about four times more efficient than incandescent lights—this is true for both the long tubes and the compact fluorescent lights CFL. See Figure 1 b. Thus, a W incandescent bulb can be replaced by a W CFL, which has the same brightness and color. CFLs have a bent tube inside a globe or a spiral-shaped tube, all connected to a standard screw-in base that fits standard incandescent light sockets.
Original problems with color, flicker, shape, and high initial investment for CFLs have been addressed in recent years. The heat transfer from these CFLs is less, and they last up to 10 times longer. The significance of an investment in such bulbs is addressed in the next example. However, their cost is still high. If the cost of electricity in your area is 12 cents per kWh, what is the total cost capital plus operation of using a W incandescent bulb for hours the lifetime of that bulb if the bulb cost 25 cents?
To find the operating cost, we first find the energy used in kilowatt-hours and then multiply by the cost per kilowatt-hour. The energy used in kilowatt-hours is found by entering the power and time into the expression for energy:. Therefore, it is much cheaper to use the CFLs, even though the initial investment is higher. The increased cost of labor that a business must include for replacing the incandescent bulbs more often has not been figured in here.
Why do incandescent lightbulbs grow dim late in their lives, particularly just before their filaments break? Explain why there is no contradiction here. What is the power of a 1. What power is supplied to the starter motor of a large truck that draws A of current from a A charge of 4.
See Figure 2. Figure 2. The strip of solar cells just above the keys of this calculator convert light to electricity to supply its energy needs. Find the power dissipated in each of these extension cords: a an extension cord having a 0.
Calculate the power of the electron beam in this tube if it has a current of An electric water heater consumes 5. What is the cost of running it for one year if electricity costs See Figure 3.
Figure 3. On-demand electric hot water heater. Heat is supplied to water only when needed. What would be the maximum cost of a CFL such that the total cost investment plus operating would be the same for both CFL and incandescent W bulbs? Calculate the cost for hours, as in the cost effectiveness of CFL example.
Some makes of older cars have 6. Alkaline batteries have the advantage of putting out constant voltage until very nearly the end of their life. A cauterizer, used to stop bleeding in surgery, puts out 2. The average television is said to be on 6 hours per day. Estimate the yearly cost of electricity to operate million TVs, assuming their power consumption averages W and the cost of electricity averages An old lightbulb draws only By what factor is its diameter reduced, assuming uniform thinning along its length?
Neglect any effects caused by temperature differences. Calculate the power loss in a kilometer of such wire when it carries 1. Cold vaporizers pass a current through water, evaporating it with only a small increase in temperature. One such home device is rated at 3.
See Figure 4. Figure 4. This cold vaporizer passes current directly through water, vaporizing it directly with relatively little temperature increase. Ignore heat transfer to the surroundings. How many cubic meters per second are needed, assuming Figure 5. Hydroelectric generators at the Hoover dam. See Figure 6. Figure 6. What is its mass per kilometer? A lower resistance would shorten the heating time. Discuss the practical limits to speeding the heating by lowering the resistance.
Find its resistance, assuming it is constant during the process. Construct a problem in which you calculate the needed resistance of the heater so that it increases the temperature of the water and cup in a reasonable amount of time. Also calculate the cost of the electrical energy used in your process.
Current, Resistance, Voltage, and Power
Current Current is a measure of the flow of electric charge through a material. A material that can carry a flow of charge is called a conductor. Current is defined as the amount of charge that flows through a conductor in a certain amount of time. The unit of current is the Ampere A , which is equal to one Coulomb per second Coulomb is the unit of charge , The symbol I is used to represent current though J is often used in engineering sources. The current I through a conductor depends on its area A , the concentration n of charge carriers, the magnitude of the charge q of each carrier, and the magnitude of their average or "drift" velocity v d , Current density is the amount of current flowing through a conductor divided by its area, The direction of the flow of current is defined in terms of a flow of positive charges even if the actual charge carriers are negative. Resistivity Some conductors carry charge more easily than others. The resistivity of a material describes how easily charge can flow.
Voltage drop is the decrease of electrical potential along the path of a current flowing in an electrical circuit. Voltage drops in the internal resistance of the source, across conductors , across contacts , and across connectors are undesirable because some of the energy supplied is dissipated. The voltage drop across the electrical load is proportional to the power available to be converted in that load to some other useful form of energy. For example, an electric space heater may have a resistance of ten ohms , and the wires that supply it may have a resistance of 0. An excessive voltage drop may result in the unsatisfactory performance of a space heater and overheating of the wires and connections. National and local electrical codes may set guidelines for the maximum voltage drop allowed in electrical wiring to ensure efficiency of distribution and proper operation of electrical equipment.
Electric Circuits 10th Pdf pdf electronic devices and circuit theory 10th edition A capacitor is a device that stores energy in the form of voltage. The Eleventh Edition of Electric Circuits represents the most extensive revision to the text since the Fifth Edition, published in In an electronic circuit, the electromagnetic problem of voltages at arbitrary points in space is typically simplified to voltages between nodes of circuit components such as resistors, capacitors, and transistors. Download Learn Electronics with Raspberry Pi.
An electric circuit is formed when a conductive path is created to allow free electrons to continuously move. This continuous movement of free electrons through the conductors of a circuit is called a current , and it is often referred to in terms of "flow," just like the flow of a liquid through a hollow pipe. The force motivating electrons to "flow" in a circuit is called voltage.
Power is associated by many people with electricity. Knowing that power is the rate of energy use or energy conversion, what is the expression for electric power? Power transmission lines might come to mind. We also think of lightbulbs in terms of their power ratings in watts. Let us compare a W bulb with a W bulb.
In an electric circuit, electrical energy is continuously converted into other forms of energy. For example, when a current flows in a conductor, electrical energy is converted into thermal energy within the conductor.
Voltage, Current, Resistance, and Ohm's Law
Track My Order. Frequently Asked Questions. International Shipping Info. Send Email. Mon-Fri, 9am to 12pm and 1pm to 5pm U. Mountain Time:. When beginning to explore the world of electricity and electronics, it is vital to start by understanding the basics of voltage, current, and resistance.
An electric circuit is formed when a conductive path is created to allow electric charge to continuously move. Voltage is a specific measure of potential energy that is always relative between two points. When we speak of a certain amount of voltage being present in a circuit, we are referring to the measurement of how much potential energy exists to move charge carriers from one particular point in that circuit to another particular point.
Это данные о сегодняшней производительности. Взгляни на число дешифровок. Бринкерхофф послушно следил за движениями ее пальца. КОЛИЧЕСТВО ДЕШИФРОВОК О Мидж постучала пальцем по этой цифре. - Я так и думала. Деление на ноль.
voltage current defines a third important quantity: resistance (more generally, Voltage is the difference in electrical potential energy of a unit of The instantaneous electric power P into a circuit element is defined.
Но честно говоря, она в это уже почти не верила. - Пусть ТРАНСТЕКСТ работает, - принял решение Стратмор. - Я хочу быть абсолютно уверен, что это абсолютно стойкий шифр.
Ну ладно, - вздохнул Стратмор. - Похоже, вышла какая-то путаница.