"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Courseware 5

Description

"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Courseware 5

Want to discuss:

Looking back at the experiment of "Measuring the resistance of a small light bulb" in the previous chapter, can you find a way to measure the electrical power of the small light bulb?

According to the formula: P=UI, by measuring the voltage across the small bulb and the current flowing through the bulb, the electrical power can be calculated.

Explore goals

Know the experimental principles

Can use voltmeter and ammeter to measure the electric power of small light bulbs

Understand rated power and actual power

Preview test

1. Clarify the purpose of the experiment

Measure the electric power of small light bulbs and explore the relationship between actual power and rated power

2. Clarify the experimental principle

P=UI

3. Determine the physical quantities to be measured

U.I.

4. Design experimental circuit diagram

In order to protect the circuit and continuously change the voltage at both ends of the small bulb to reach a certain value, a sliding rheostat is added.

Experimental steps:

1. Turn off the switch, connect the circuit according to the circuit diagram, and adjust the sliding blade of the sliding rheostat to the maximum resistance value.

2. Close the switch, adjust the voltage to the normal working voltage of the small bulb (2.5V) through the sliding rheostat, record the U and I values, and observe the brightness of the bulb.

3. Make the voltage at both ends of the small bulb approximately 1.2 times the rated voltage. Observe the brightness of the small bulb and record the data.

4. Make the voltage at both ends of the small bulb lower than the rated voltage, observe the brightness of the bulb and record the data.

analysis argument

1. Compare the actual power you measured with the rated power of the small light bulb. Are they necessarily equal?

2. Will the brightness of the light bulb be the same under different actual powers?

3. What do you think determines the brightness of a small light bulb?

Exchange and display

The actual electrical power consumed by the small light bulb is not necessarily equal to the rated power.

When the small light bulb U is equal to U, P is equal to P; it emits light normally.

When the small bulb U solid > U forehead, P solid > P forehead; brighter

When the small light bulb U solid < U amount, P solid < P amount; darker

The brightness of a small light bulb is determined by its actual power

Feedback exercise: Analyze the causes of the following experimental phenomena

Phenomenon 1: Xiaocheng connected the experimental circuit, closed the switch, and found that the pointer of the voltmeter was reverse biased.

Analysis:

The "+" and "-" terminals of the voltmeter are connected reversely.

Phenomenon 2: In the experimental circuit connected by Xiao Huang, when the switch is closed and the slider is moved, the brightness of the bulb changes significantly, but the pointer of the ammeter swings small and it is difficult to read the current value.

Analysis: The range of the ammeter selected is too large. The current of small light bulbs is generally less than 0.6A, so the range of 0~0.6A can be used.

Phenomenon 3: In the experimental circuit that Xiaoyang connected, the rheostat and the light bulb were connected in series, but when the switch was closed, the small light bulb was found to be particularly bright.

Analysis:

1. The sliding rheostat is not adjusted to the maximum resistance before closing the switch.

2. This situation will also occur if the upper two terminals of the sliding rheostat are connected to the circuit at the same time.

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For more information about the PPT courseware "Electrical Power Measuring the Electric Power of Small Light Bulbs", please click the Electric Power ppt Measuring the Electric Power of Small Light Bulbs ppt tag.

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Update Time: 2024-11-18

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