"Electric Power" PPT Courseware 2

Description

"Electric Power" PPT Courseware 2

Self-study test

1. In physics, ___ is used to represent the speed of work done by electric current. Electric power is represented by ___, the unit is ___, abbreviated as ___, and the symbol is ___. The unit larger than it is ___, the symbol is ___, the unit smaller than it is ___, the symbol is ___.

2. 1kW=___W=___mW.

3. The definition of electric power is ___.

collaborative inquiry

1. What is the difference between the change in the reading of the electric energy meter when using an electric kettle to boil water and the change in the reading when using an ordinary light bulb for lighting? what have you found? What does this mean?

When using different electrical appliances, the speed of the change of the electric energy meter's indication (the speed of the rotation of the aluminum disk) is ______.

This shows that different electrical appliances consume electricity at different ______ speeds. That is to say, current flows through different electrical appliances at different speeds.

2. Review: How does the speed of work done by a force be expressed? So what is the expression of how fast the current does work?

Expressed by ______. The speed of work done by electric current should be expressed as ______.

5. Think about how the power formula you learned in eighth grade is defined, discuss and derive the definition of electrical power.

The ratio of work to the time taken to do the work is called power----P=W/t.

The ratio of electrical power to the time used is called electrical power----P=W/t,

Substituting W=UIt into the above equation, we can get P=UI.

6. Summary:

The calculation formula of electric power: P=W/t, P=UI.

Relevant derivation formulas: W=Pt, t=W/P, U=P/I, I=P/U.

Instructions and advice

1. When using the above formula for calculation, all units must correspond one to one.

2. We already know that P=UI, P=W/t, and we also know that U=IR. If we combine these three sets of formulas, what new derivation formulas can be obtained?

P=U2/R，P=I2R，R=U2/P，R=P/I2

instant practice

1. The nameplate of an electric kettle is marked with "220 V 1 000 W". What is the current when it is working normally?

Solution: Current during normal operation

I=P/U＝1000W/220V＝4.5A

Self-study test

1. From the formula P=W/t, we can get W=___. If the unit of P is ___ and the unit of t is ___, then the unit of W is ___. Referred to as___.

2. 1kW·h of electric energy is equivalent to the electric energy consumed by an electrical appliance with a power of ___.

3. The voltage when the electrical appliance is working ___ is called ___ voltage, and the power when the electrical appliance is working at ___ voltage is called ___ power.

4. The voltage when the electrical appliance is actually working is called ___ voltage, and the power when the electrical appliance is working under the actual voltage is called ___ power.

5. When using various electrical appliances, make sure they work at rated voltage. If the actual voltage is too high, it may ______. If the actual voltage is too low, the electrical appliance may not work normally.

collaborative inquiry

1. Complete the examples independently and tell me, what should you pay attention to when calculating?

Example: The electrical power of a TV set is 150 W (Figure 18.2-2). If it is used for 3 hours a day, how many kilowatt hours of electricity is used in a month? (Calculated based on 30 days)

Solution: P= 150 W = 0.15 kW

t = 3 h × 30 = 90 h

Deformed from P=Wt, we get W = Pt

The electricity consumed in a month is

W = Pt = 0.15 kW × 90 h = 13.5kW · h

Note: When calculating, the units must be unified. Only the unit of power is kW, the unit of time is h, and the unit of the final electric energy is kW·h.

2. Discuss as a group "I want to discuss" on page 93 and tell me where this reporter went wrong? What should be the correct statement? Please do the math.

When a TV reporter talked about a factory that saved a total of 5,000kW·h in the first half of the year, he held up a hair dryer for haircuts and said: "My hair dryer is 500 watts, which is 0.5 kilowatts. The power saved by this factory You can run 10,000 of these hair dryers." Where did this reporter go wrong?

This reporter's mistake: confused the relationship between (electric energy) kW·h and (electric power) kW.

The correct statement is:

The time that this electric energy can allow a hair dryer with a power of 0.5 kW to work normally is t=W/P=5000kW·h/0.5kW=10000h

collaborative inquiry

1. As a group, discuss and design an experimental plan for measuring the electric power of a small light bulb to prepare for the experiment in the next class.

2. Discuss the designed plan with each other within the group. Compare whose experimental plan is the simplest and most effective.

Instructions and advice

Two ways to measure electrical power:

1.P=UI

2.P=W/t

Keywords: Electric power teaching courseware, New People's Education Edition ninth-grade physics PPT courseware, ninth-grade physics slide courseware download, Electric power PPT courseware download, .ppt format

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Update Time: 2024-09-10

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