"Special Method for Measuring the Electric Power of Small Light Bulbs" Electric Power PPT

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"Special Method for Measuring the Electric Power of Small Light Bulbs" Electric Power PPT

Topic overview

The conventional experimental method for measuring electrical power is voltammetry, which uses a voltmeter and an ammeter to measure the voltage at both ends of the electrical appliance and the current passing through the electrical appliance respectively, and calculate the electrical power according to P = UI; due to limitations of the measuring equipment, in the absence of a Under the conditions of the instrument, a certain physical quantity cannot be measured directly. At this time, the measurement of the physical quantity can be completed with the help of a fixed-value resistor or resistance box. Commonly used methods include the volt resistance method, the ampere resistance method, and the substitution method.

Type 1: Measuring the electrical power of electrical appliances using the volt resistance method

1. Use a voltmeter and a fixed-value resistor with a known resistance to measure the electric power of the small bulb. When measuring, as shown in Figure 2-ZT-1, connect the bulb in series with a resistor with a known resistance R0, and use a voltmeter to Measure the voltage U1 across the resistor R0 and find the current I through R0, that is, the current through the light bulb is I = ________. Then use a voltmeter to measure the voltage U2 across the light bulb. Use the formula P = UI to find out the Electric power P = ________.

2. Use the circuit shown in Figure 2-ZT-2 to measure the rated power of the light bulb. The small light bulb is marked with "2.5 V" and the resistance value of R0 is known.

(1) Complete the experimental process:

A. Connect the circuit according to the circuit diagram, and slide the sliding piece of the sliding rheostat to the maximum resistance value.

B. Close the switch, __________________________________________________.

C. Turn off the switch and organize the equipment.

(2) The expression for the rated power of a small light bulb: P = ________. (Represented by symbols for measured quantities and known quantities)

(3) Write the function of the sliding rheostat in this experiment: ____________________________________________.

3. In the "Measuring the rated power of a small light bulb" experiment, the light bulb is marked with "3.8 V" and the power supply voltage is constant.

(1) Please use pen lines instead of wires to completely connect the physical circuit in Figure 2-ZT-3A.

(2) After connecting the experimental circuit, when using the switch to test, it was found that the bulb did not light up, the ammeter showed almost no reading, and the voltmeter showed close to the power supply voltage. The cause of the failure may be ____________________.

(3) After the fault is eliminated, start the experiment. During the process of moving the sliding varistor slide, your eyes should watch the indication of _______ until the light bulb lights up normally. At this time, the indication of the ammeter is as shown in Figure B, and the indication of the bulb is The rated power is _______W.

(4) After completing the above experiment, Xiao Cong borrowed a resistor with a known resistance value R0 and a single-pole double-throw switch from the teacher. With the help of some existing experimental equipment, he designed the circuit as shown in Figure C and also tested out the wattage rating of the bulb. Please complete the following lab steps:

① Close switch S1, move S2 to contact 2, and move the slider so that the voltmeter reads ________V;

② Then move switch S2 to contact 1, keep the position of the slider still, and read the indication U of the voltmeter;

③The expression for the rated power of the light bulb is P = ________. (expressed using symbols for known and measured quantities)

Type 2: Measuring the electrical power of electrical appliances using the anmpere-resistance method

4. Use an ammeter and a fixed-value resistor with a known resistance to measure the electric power of the small light bulb. When measuring, as shown in Figure 2-ZT-4, connect the light bulb in parallel with a resistor with a known resistance R0, and use ammeter A1 to measure it. Detect the current I1 passing through the resistor R0, and use ammeter A2 to measure the current I2 passing through the bulb L. The voltage across R0 is: U = ________, and the electric power of the bulb: P = ________.

5. (Multiple choice) As shown in Figure 2-ZT-5, several students used a resistor R0 with a known resistance to design four circuits for measuring the electrical power of the unknown resistor Rx when they only had an ammeter. Among them, it was not feasible ()

6. In order to measure the rated power of the small light bulb marked with "2.5 V", a student designed the circuit diagram shown in Figure 2-ZT-6A, in which the resistance of the fixed-value resistor R0 is 5 Ω.

(1) Please use strokes instead of wires according to the circuit diagram to complete the connection in Figure B. (Wires must not cross)

(2) After the circuit is correctly connected, close the switch S and adjust the slider of the sliding rheostat so that when the ammeter A1 reads ________A, the small bulb lights normally. At this time, the indication of ammeter A2 is as shown in Figure 2-ZT-7, then the rated power of the small light bulb is ________W.

(3) During the experimental measurement process, the function of ammeter A1 and R0 in series is equivalent to ________.

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For more information about the PPT courseware "Measurement of Electric Power of Small Light Bulbs by Special Electric Power Methods", please click the "Measurement of Electric Power of Small Light Bulbs by Special Electric Power ppt" tag.

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Update Time: 2024-09-27

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