1, as shown in the figure, is a kind of light bulb commonly used in families, and the nameplate on the light bulb.
(1) According to its nameplate, what physical quantities can be known?
(2) According to the information on the nameplate, what other physical quantities can be known through calculation? Calculation instructions.
(3) How many hours can this bulb work with L-degree power?
2. As shown in the figure, it is a schematic diagram of the nameplate layout of the electric energy meter in a classmate's home circuit.
(1) If the specification of the lighting bulb is "220V, 60W", two sockets are connected to a "220V, 10ow" TV set, and three hole socket is connected to a "220V, 280W" rice cooker, what is the current through the electric energy meter when they both work?
(2) If the electric lamp and TV set are used for 5h and the rice cooker is used for 1h on a certain day, how much KW will be consumed that day? H's electricity
(3) If the classmate bought an electric water heater with the nameplate "220V, 1 100W" at home, he wanted to test whether the marked power was consistent with the actual power, so he let the electric water heater work independently and use the watch to time, and the turntable of the 10min electric energy meter turned 280r r. Please calculate the actual power of the electric water heater.
3. As shown in Figure 3, the radio kettle (a convenient kettle with electric heating when pouring water) commonly used in families and hotels, and the nameplate of the electric kettle is on the right side of Figure 3. A classmate uses this electric kettle to boil water. He put the water to the maximum, and measured the temperature of the water as 18℃. After being electrified for 5min and 50s, the water boiled (under standard atmospheric pressure). Try to answer the following questions by calculation:
1) Calculate the current when the electric kettle works normally.
2) What is the resistance of the electric kettle?
3) The measured power supply voltage is 2 10V. Calculate the working efficiency of this electric kettle.
4) In order to measure the efficiency of the radio kettle, what experimental equipment should be prepared?
4. Read the following materials and answer the questions:
On June 4, 2005, the Huygens probe launched by the European Space Agency landed on Titan 6, Saturn's largest satellite, which is 0/0/0.5×/0.09 km away from the Earth. It is reported that the probe looks like a glowing meteor after entering Titan's atmosphere. The probe approaching Enceladus 6 has opened three deceleration parachutes and slowed down until it landed safely. After landing, the detector sent back the radio signal of safe landing to the control center on earth.
(1) Why does the detector look like a shining meteor after entering the atmosphere?
(2) How do the kinetic energy and potential energy change during the deceleration and landing of the probe?
(3) How many seconds does it take for the detector to transmit the collected information to the earth by radio waves? (The propagation speed of radio waves is 3× 105 km/s)
5. There is an electronic scale for measuring people's weight and height, and the schematic diagram of the weight measurement part is shown in the dotted box in the figure. It is mainly composed of three parts: pedal and pressure bar ABO, pressure sensor R (variable resistance whose resistance will change with pressure), and meter A (ammeter in essence) for displaying weight. Where ao: bo = 5: l, the maximum pressure on the surface of pressure sensor R is 2× 106pa, and the relationship between resistance and pressure of pressure sensor R is shown in the following table.
Pressure f/n o 50100150 200 250
Resistance r/ω 300 270 240 2lo180150.
Assuming that the mass of the pedal and lever assembly can be neglected, the voltage across the pressure sensor is constant at 4.68 V after the power supply is turned on, and g = 10N/kg. Please answer:
(1) How many milliamperes should the scale mark at the zero starting point of the scale (that is, when the pedal is empty) be marked on the ammeter dial?
(2) If someone stands on the pedal of weighing scale, and the dial of the ammeter reads 20mA, what is the person's weight?
(3) If the contact area between the pressure bar and the pressure sensor is 2cm2, what is the maximum weighing value of the scale?
6. When cooking breakfast, Xiaolan found that boiling a pot of milk is faster than boiling the same amount of water under the same circumstances. Why? Please use your knowledge of physics to make a guess about the reason and briefly describe the method to verify this guess.
1) Your guess is:
2) The method to verify the conjecture is:
7. In the activity of science and technology group, an electronic scale was designed, and its principle is shown in the figure. He tried to reflect the mass of the object with the reading of a voltmeter (not shown in the figure). Let the power supply voltage be constant U, and the resistance value of the constant resistor be R. The total resistance of the sliding rheostat is R, and the total length is L. The sliding contact is fixed on the light spring of the tray and can slide freely with the light spring. It is known that every time a pressure of 1N is applied to the tray, the length of the spring will be shortened by a. When there is no object in the tray, the sliding contact will move down to a certain position with the spring, so the voltmeter will indicate the corresponding indication.
(1) If an object with a mass of m is placed on the tray, how far does the sliding contact move down?
(2) Please connect a voltmeter that meets the requirements at an appropriate position in the schematic diagram.
(3) Find the relationship between the indicator U of voltmeter and the mass m of the measured object (represented by the symbol of known quantity).
8.AB and CD are exactly the same two insulated wires, buried in parallel between A and B which are 2km apart. Because the insulation sheath somewhere between the two wires is damaged, leakage occurs (that is, a resistor is connected between the two wires at the leakage point), as shown in the figure. When determining the location of the leak, the maintenance personnel made the following measurements:
(1) Connect a power supply with a constant voltage of 90V to terminals A and C respectively. At this time, at point B, the voltage across B and D is measured to be 72V with a voltmeter with large internal resistance.
(2) At the second place, the two ends of B and D are respectively connected with the two poles of power supply with constant voltage of 100V, and the voltage at the two ends of A and C is 50V measured by the first voltmeter of the same model.
If the resistance of AB line and CD line is 2 Ω per kilometer, please calculate the leakage distance from A to ground according to the above measurement results. What is the leakage resistance of damaged insulation?
9. The household microwave oven is a cooker that uses microwave electromagnetic energy to heat food. It is mainly composed of magnetron, waveguide, microwave heater, oven door, DC power supply, cooling system, control system and shell. Microwave is a kind of radio wave, and its corresponding frequency is 30 000 MHz ~ 300 MHz. When the power supply is turned on, the magnetron will generate microwaves with a frequency of 9 15MHz or 2450MHz. It reflects back and forth in the metal furnace cavity, and the electromagnetic action of microwave makes the food molecules vibrate at high frequency, and the inside and outside heat up rapidly at the same time, which can maximize the preservation of life-sustaining cables in food.
The power of (1) magnetron is 700W, and the efficiency of food absorbing microwave electromagnetic energy is 90%. How much energy does the food absorb if it is heated for 2 minutes?
(2) When microwave is used to heat food, there are ceramic containers, metal containers and plastic containers. Which container should you choose? Why?
(3) Besides heating, what other applications are there for microwave?
(4) Like other electromagnetic waves, overexposure is harmful to human body. What measures can be taken to ensure that the microwave leakage does not exceed the allowable value?
(5) What is the wavelength range of microwave?
(6) The working frequency of microwave ovens is mostly 9 15MHz or 2 450MHZ. Why?
10, a small DC motor, its coil internal resistance is 20 Ω, connected to a power supply with a voltage of 200V V. Please answer the following questions: (1) What is the working principle of the motor? (2) What is the maximum output power of the motor when the current input to the motor is large? What is the maximum output power? (3) When the motor is at the maximum output power, what is its efficiency? It can lift multiple objects and rise at a speed of 2m/s?