2. The light bulb of "PZ 220-25" is connected in a 220 volt circuit. What is the current flowing through the light bulb? How big is the bulb resistance at this time? If the light bulb is connected to a 2 10 volt circuit, what is the actual output power?
3. The resistance of resistor R 1 is10Ω. When resistors R 1 and R2 are connected across the power supply in some way, the voltage across R 1 is 9V. When two resistors are connected across the same power supply in another way, the voltage across R 1 is 3V. Find the resistance of R2.
4. The known power supply voltage is 10V. If a bulb and a sliding rheostat are connected in series in the circuit, the voltage at both ends of the sliding rheostat is 4V and the current flowing through it is 2A, so find the resistance of the bulb.
1. Xiaoming has an electric furnace marked "220V, 800W", and a pot of water can be boiled at rated voltage 10 minute. One day, he used this electric stove to boil the same pot of water in the same environment (air temperature and pressure are the same), and it took 12 minutes. Please help Xiao Ming calculate what the power supply voltage was at that time. What approximate conditions did you use in the calculation?
2. When doing electrical experiments, it is necessary to measure the current of about 0.5 A, but at that time there was only one ammeter with a range of 0.3 A in the laboratory. If you have a 12 V student power supply, a 0 ~ 50 ohm sliding rheostat, electric furnace resistance wires, wires and switches at hand, is there any simple way to temporarily approximate the range of the ammeter to 0.6 A? Draw a circuit diagram and briefly describe the operation steps.
Xiaofang has an electric kettle for boiling water, and the nameplate reads "220V, 1000W". Please help her design a method to measure the efficiency of this kettle when boiling water. Write out the equipment used, measurement steps and deduce the calculation formula.
There is a waterfall. Every minute, 60 meters of water falls from 50 meters high. I want to use it to build a small hydropower station. If 70% of the mechanical energy of water is converted into electrical energy, and the transmission voltage is 10000 volts, what is the current on the conductor? (g = 10N/kg)。
5. The distance between A and B is L, during which a telephone line consisting of two wires is laid. The resistance per unit length of a single wire is R (the unit of R is ohm/meter), and the terminal of B is connected with a load resistance. If the insulation layer in the middle of the line is damaged, two lines are connected. In order to find out the connection position, I will give you a direct regulated power supply with a voltage of U and an ammeter with a suitable range. How to find the distance and contact resistance from the damaged part to the damaged part?
6. When the power consumption of the lighting circuit reaches the peak, the lamp will dim, because the voltage across the lamp decreases. A classmate wants to measure the actual voltage at both ends of the lamp, but there is no AC voltmeter at hand, only a watch, an electric soldering iron with nameplate, and a running watt-hour meter with nameplate on the switchboard. He used these devices to calculate the actual voltage across the electrical appliances in the lighting circuit. Please explain his calculation method.
7. There are two kinds of light bulbs, which are labeled as (1 10V 60W) and (1/0V25W) respectively. Connect them to the home lighting circuit.
(1) Can one of them be used in series? Please explain the reason.
(2) If two kinds of bulbs are mixed in the same circuit and both can emit light normally, how many bulbs should be used at least and how to connect them?
(3) What is the total electric power at this time?
8. Three of the four resistors with the same appearance have the same resistance. In order to pick out the resistors with different resistances and determine whether their resistances are too large or too small, Xiaohua designed the circuit as shown in the figure. After closing the switch, he found that the current flowed from Q to P, and the galvanometer pointer was deflected to the right. Please help him finish the experiment and answer how he got the result. (It is required to write the experimental operation process, and the process should be as simple as possible.
9. At present, the power supply system of new buildings no longer uses fuses, but uses automatic control safety circuits. When the electric load is too large or a short circuit occurs, the circuit will be automatically cut off; If a person standing on the ground touches the fire line, and the fire line and the earth pass through the human body, the circuit will be automatically cut off to ensure personal safety.
Xiaoling has installed this kind of circuit in her new house. After moving, she saw that the power socket on the wall was three-wire. In order to install the TV, she bought a patch panel, plugged it into a three-wire socket on the wall, and then plugged the TV into the socket on the patch panel. But when the TV is turned on, all the sockets in the room are cut off, indicating that the circuit is automatically cut off. When I looked at the distribution box, it was indeed a "trip" (the main switch automatically cut off).
Is there something wrong with the TV set, and it consumes too much power? Turn off the main switch by hand, and plug several other electrical appliances that can ensure normal operation into this plug board until the small desk lamp only consumes 15 watts, or so. However, plug the latch plate into other jacks on the wall, and everything is fine. What could be the problem? Why is this happening? How to solve it?
10. 1996 students from Tsinghua University and hongkong university jointly developed a solar car. The area of the solar receiving plate of the vehicle battery is 8m2. When it is facing the sun, the battery can generate a voltage of 120V and provide a current of 10A to the automobile motor. The DC resistance of the motor is 4Ω, and the radiation power per unit area is 65430 when the sun shines on the ground.
1. What is the solar cell efficiency of this car? How efficient is the motor to convert electrical energy into mechanical energy?
2. If the total solar radiation power is 3.9× 1.026 W and the energy loss of sunlight on the way through space and the earth's atmosphere to the ground is 28%, it is also known that the spherical area with radius r is S = 4 π R2. Please calculate the distance from the sun to the earth according to these data.
1 1. The total power of the generator set of Liujiaxia Hydropower Station is 1.225× 10 to the 6th power kw.h. If the annual output power is 5.7× 10 to the 9th power kw.h, what is the total working time of the generator set?
12. Wind is caused by solar radiation. The sun shines on the earth's surface, and different parts of the earth's surface are heated, resulting in temperature difference, causing atmospheric convection and forming wind. It is estimated that although only about 2% of solar energy reaching the earth is converted into wind energy, its total amount is still considerable. The global total wind energy power is about 2.74× 10 12KW, of which the available power is 2./kloc-0 /× 10kw, which is10 times larger than the total amount of water energy that can be developed and utilized on the earth. The energy obtained by burning coal every year in the world is less than 1% of the energy provided by wind power. It can be seen that wind energy is one of the important energy sources on the earth.
Compared with other energy sources, wind energy has obvious advantages and outstanding limitations. Wind energy has four advantages and three disadvantages. The four advantages are: (1) huge accumulation; (2) it can be regenerated; (3) Widely distributed; (4) no pollution. Three weaknesses are: (1) low energy density; (2) poor stability; (3) There are great regional differences.
Question:
(1) If the combustion value of coal is 3.0× 107J/Kg, please calculate how many tons of coal are burned every hour in the world according to the above data. (The result shall be 1 digit after decimal point)
(2) If the efficiency of converting wind energy into mechanical energy is 40% and the efficiency of converting mechanical energy into electrical energy is 50%, how many kWh of electrical energy can be obtained from the global available wind energy 1 hour? 10℃ How many tons of water can these electric energy increase? (The result shall be 1 digit after decimal point)
(3) If wind energy can be fully developed and utilized, it will play a great role in world energy conservation and environmental protection. But in China, wind energy has not been widely used. Please talk about the reasons according to the relevant knowledge you know. (Answer only one reason)
13. During the construction of the construction site in mountainous areas, the lighting lines should be connected from the power supply 250 meters away from the construction site, and "220V 100W" and "220V 200W" bulbs should be used for the construction site lighting. The resistance of the wire used is 0.0 18 ohm per meter. If the voltage across the power supply is 20, (the change of filament resistance is not considered in the calculation, and the value is only an integer, and the decimal can be rounded off.
14. The students in the extracurricular activity group designed and made an electric incubator. They use two heating wires with the same rated voltage and power as the heat source, and then connect a resistor R0, so that even if one heating wire is broken, the heat generated by a single wire is still exactly the same as that generated by a double wire. If the voltage across the power supply is U, the rated voltage of the two wires is UL and the rated power is PL.
(1) Draw the circuit diagram of the incubator. (2) What is the resistance of 2)R0?
(3) What is the power consumption ratio of 3)R0 under single-wire operation and double-wire operation?
15. The water temperature in the water tank is often not high enough in winter. The students installed a "220 V, 2000 W" electric heating tube in the water tank, and installed an indicator light for the electric heating tube with a "6 V, 1W" light bulb and a section of10 Ω/m resistance wire.
(1) Draw the electrical schematic diagram of the electric heating tube and indicator lamp.
(2) In the student scheme, the voltage at both ends of the small light bulb is designed as 5V. What are the benefits of this design for the indicator light?
(3) According to the above design, how long should the resistance wire be cut?
(4) After the indicator lamp is installed, what percentage of the rated power is the actual power of the electric heating tube?
16. The DC motor used on the machine tool is marked with the words "36V, 24W". The resistance of the motor measured by multimeter is 2 Ω. Try to calculate the efficiency of this motor when it is fully loaded.
17. Rechargeable batteries are usually used in mobile phones, digital cameras and other electrical appliances. The voltage and capacity marked on the battery are two important parameters. The unit of capacity is usually "milliampere hour" (symbol MA. h)。 The marked voltage of a rechargeable battery is 1.2V, and the capacity is 1300mA? Please estimate the electric energy that this battery can store.
18. When measuring current and voltage with ammeter and voltmeter, the influence of the resistance of the instrument itself on the circuit under test is usually not considered, and it is regarded as an "ideal instrument", that is, the internal resistance of ammeter is zero and that of voltmeter is infinite. In fact, both ammeter and voltmeter have certain resistance values, so we can regard ammeter as a resistance with small resistance, which can display the current through itself. The voltmeter can be regarded as a resistor with great resistance, which can display the voltage across itself. Therefore, when an ammeter or voltmeter is connected to the circuit under test, it is equivalent to connecting a resistor in series or in parallel in the circuit under test. In this way, there must be a certain voltage on the ammeter and a certain current on the voltmeter, so it is difficult to accurately measure the voltage on the measured resistor and the current through the measured resistor at the same time.
1. has an ammeter with a measuring range of 0.6A and an internal resistance of 0. 13 ohm. Can it be used to measure the negotiated voltage of a circuit? If not, please explain why. If yes, please explain the maximum voltage that can be measured with it.
2. In order to accurately measure the resistor Rx with a resistance of about 8 ohms, the laboratory provides the following equipment.
The ammeter A 1: range 100mA, internal resistance r 1 = 4ω.
Amperometer A2: The measuring range is 500μ α, and the internal resistance R2 = 750ω.
Voltmeter v: range 10V, internal resistance r3= 10k ohm,
Varistor R0: The resistance value is about 10 ohm.
Fixed value resistance R 1: the resistance value is about 10k ohm.
Battery e: voltage at both ends 1.5V or so, switch s, several wires.
(1) Select the appropriate equipment needed for measurement and draw the circuit diagram.
(2) What physical quantities need to be measured? According to the measured physical quantity, write the expression of the measured resistance Rx.
19. The students in the science and technology group are going to conduct quality inspection on a batch of light bulbs marked "PZ 220V- 100W" in the market. They measured the actual current value of the bulb at different voltages (see the table below). The experiment runs reliably and the data is correct.
Voltage u/v ...180185l90195 200 205.
Current I/A ... 0.417 0.426 0.434 0.438+0 0.447 0.4433.10000000001
Voltage u/v 210 215 220 225 230 235 240
Current I/A 0.458 0.462 0.467 0.47L 0.475 0.479 0.482
Please answer:
(1) Try to explain by calculation whether the power consumed by this bulb is equal to the rated power when it works at the nominal voltage.
(2) If the thickness of the tungsten wire used to produce this kind of bulb is fixed and the length of the tungsten wire is a certain value l0, is it actually longer or shorter than l0 in order to make the power consumed when it works at the nominal voltage equal to the rated power? Why?
(3) If this bulb is to reach the rated power, what should be the actual voltage applied to the bulb L?
Tip: It can be used as a method solution for images. Make relevant images on the coordinate paper of 10, and get the results according to the images. (Figure 10 is a common coordinate axis, so you can't upload it, just draw one yourself. )
Li Ming's classmate wants to buy a kettle for boiling water. There are two kinds of aluminum pots with the same capacity but different varieties in the supermarket. One is used on a liquefied gas stove, and the other is equipped with an electric heater. Li Ming wants to compare which kettle is more economical to boil water He first conducted an investigation and got the following information: the electricity price of local residents is 0.5 yuan/kWh; The price of bottled liquefied gas is 60 yuan/bottle (the mass of each bottle of liquefied gas is about 15 kg, and the calorific value of liquefied gas is 4.2×107j/kg); The thermal efficiency of boiling water with liquefied gas is about 30%, and that of boiling water with electric kettle is about 90%. According to the above information, please calculate and analyze which kettle is more economical to use for boiling water.
Download the ninth grade physics test paper:
/upload/forum/2005112354444.doc
/per admin/html file/sly 6807/2007022 10757072677078 . doc