"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Courseware 8

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"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Courseware 8

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Commonly used small light bulbs are marked with rated voltage (such as 2.5 V, 3.8 V), but not with rated power. For example, the rated voltage of a small light bulb is 2.5 V. How to measure its rated electrical power?

student experiment

The purpose of the experiment is to measure the electrical power of small light bulbs.

Experimental principle P = UI.

Experimental equipment: power supply, switch, wires, ammeter, voltmeter, sliding rheostat, small light bulb (rated voltage 2.5 V).

Please draw the experimental circuit diagram according to the experimental principle.

Experimental requirements

(1) Move the slider of the rheostat so that the voltages at both ends of the small bulb are rated voltage, lower than rated voltage, and higher than rated voltage (about 1.2U).

(2) Record the voltage value and current value, and observe the difference in brightness of the comparison lamps.

Tip: Pay attention to the range of the ammeter and voltmeter, and the use of the sliding rheostat.

Experimental steps

(1) Set the pointers of the voltmeter and ammeter to zero, turn off the switch, connect the circuit according to the circuit diagram, and place the slider of the sliding rheostat where the resistance is maximum.

(2) Close the switch and adjust the slider of the sliding rheostat so that the voltage indication numbers are 2.5V, 2V and 3V in sequence. Record the voltage indication number U and the corresponding current indication number I in sequence, and record U and I in the table respectively;

(3) Observe and compare the lighting conditions of the three small light bulbs, and record the phenomena in the table.

Comparison of lamp brightness

Demonstration experiment 1:

Lamp A is marked with "PZ 220 V 40 W" and lamp B is marked with "PZ 220 V 100 W". The two lamps are connected in parallel in a 220 V circuit and the brightness of the two lamps is compared.

Conclusion: When U real = U forehead , the light bulb with the largest P forehead will light up.

Demonstration experiment 2:

Connect the above two lamps in series in a 220 V circuit and compare the brightness of the two lamps.

Conclusion: When U real ≠ U amount , the light bulb with the smaller P amount will light up.

To compare the brightness of two lamps, their actual wattages should be compared. The bulb with the larger actual wattage will be brighter.

practice

1. Use the equipment as shown in the figure to measure the electrical power of the small light bulb.

(1) Before closing the switch, the resistance value of the sliding rheostat connected to the circuit should be the highest ___, that is, the slider should be located at the ____ end (fill in "left or right").

(2) After closing the switch, it is found that the bulb does not light up, the voltmeter has a reading, but the ammeter does not, then the possible fault in the circuit is _________.

(3) After troubleshooting, close the switch again and move the slide of the sliding rheostat. When the voltmeter indicates 2 V, the ammeter indicates as shown in the figure. At this time, the current is ____A and the power of the small bulb is ___W.

2. The small light bulb is marked with "6 V 3 W". When the light is connected to 3 V, it will emit light ___ (optional "brighter" or "dark") than when it normally emits light. At this time, its actual power is _____W.

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Update Time: 2024-06-29

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