"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Courseware 3

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"Measuring the Electric Power of Small Light Bulbs" Electric Power PPT Courseware 3

Self-study test

1. The principle of this experiment: ______.

2. We use ______ to measure the voltage across the small bulb and ______ to measure the current flowing through the small bulb.

3. Design and draw the experimental circuit diagram.

collaborative inquiry

1. Group discussion:

1. What experimental equipment and tools are needed to complete this experiment?

Battery pack, switch, several wires, ammeter, voltmeter, sliding rheostat, small light bulbs of different specifications.

2. What role does the sliding rheostat play in this experiment? To what position should the slide be moved before closing the switch? How to move the slide more effectively?

The functions of the sliding rheostat: 1. ______; 2. Change the ____ at both ends of the bulb and the ____ in the circuit, and perform multiple measurements.

Before closing the switch, the slider should be located at the highest resistance point, and then move from the highest resistance point to the end with a higher resistance.

3. How should the ammeter and voltmeter be connected to the circuit?

The ammeter is connected in series in the circuit and the voltmeter is connected in parallel across the small bulb.

4. Observe the specifications of the small light bulb provided by the teacher. In order to prevent the voltage from exceeding the rated voltage too much, what should be the voltage across the power supply during the experiment? How many dry batteries are used in series to provide power?

The rated voltage of the small light bulb provided by the teacher is __. The power supply voltage in the experiment should be __, and __ dry batteries are used in series for power supply.

2. Do it yourself.

According to the designed circuit diagram, work as a team to connect the physical diagram, check the experimental circuit, close the switch, complete the experiment, and record the experimental results in the above table.

3. Do the math

Use the formula P=UI to calculate the corresponding power and fill it in the table above.

4. Compare

Are the actual power and brightness of small light bulbs the same at different voltages? Observing the above table, what do you think the actual power of the small light bulb depends on?

Under different voltages, the actual power and brightness of small light bulbs are different.

When the actual voltage across the small bulb exceeds the rated voltage, the small bulb emits ____; when the actual voltage is equal to the rated voltage, the small bulb ____ emits light; when the actual voltage is lower than the rated voltage, the small bulb emits ____; so the small bulb The actual power depends on the _________ at both ends.

Instructions and advice

1. Only when the actual voltage is equal to the rated voltage, the actual power of the electrical appliance is equal to the rated power.

2. Think:

In the above experiment, can the average power of the small light bulb be calculated based on the calculated three times power? Why?

Answer: ______ do this because the power of the small light bulb will change with the change of the voltage at both ends. It is not a fixed value. It is meaningless to average multiple measurements.

3. Can the power of household appliances be measured using the formula P=W/t? If so, what experimental equipment is needed and how should it be done? Ask students to discuss and write down the experimental principles and procedures.

Analysis: Because P=W/t, according to this formula, to measure the power of household appliances, it is necessary to measure ____________ and ____________. We can use ____________ to measure W and __________ or __________ to measure t.

Steps: Turn off other electrical appliances in the home, let only the electrical appliance under test work, let it work for five minutes, and record the number of revolutions n of the aluminum plate.

calculate:

Electric energy consumed W=n÷number of revolutions/kWh

Electrical power of the electrical appliance under test P=W/t

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Update Time: 2024-07-02

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