"Electric Power" PPT courseware 5

Description

"Electric Power" PPT courseware 5

Review and Reflection

1. What is the unit of electrical energy? What's the conversion relationship?

2. Instrument for measuring electrical energy – energy meter

So far, 823.6 kilowatt-hours of electricity have been consumed.

220V—Indicates that the rated voltage of this electric energy meter is 220V.

10 (20) A—Indicates that the maximum current allowed by this energy meter is 10A (cannot exceed 20A in a short period of time)

50Hz - Indicates that the energy meter is used in a 50Hz AC circuit

1500r/kW·h - means that for every 1kW·h of electric energy consumed, the energy meter's turntable rotates 1500 times

Observation experiment: Connect 60W and 25W light bulbs in parallel in the circuit to make them emit light normally and observe the brightness.

Conclusion: The aluminum disk of the electric energy meter rotates at different speeds, which means that the electrical appliances consume electricity at different speeds.

The faster the electric energy meter rotates, the faster (cannot say more) the electrical energy consumed by the electrical appliance; conversely, the slower the electrical energy consumed by the electrical appliance.

learning target

1. Know that electrical power is a physical quantity that indicates the speed of electrical energy consumption.

2. Know the concepts, formulas and units of electrical power.

3. Know the origin of the kilowatt-hour unit of electrical energy.

4. Know the rated power and rated voltage, and be able to distinguish between rated power and actual power.

5. Understand the relationship between electrical power, current, and voltage, and perform simple calculations.

1. Electric power

Read textbook P91-92 and answer the following questions:

1. Physical meaning: Indicates how fast the current does work. Or the speed of power consumption

2. Unit: watt, referred to as watt, symbol is W.

Commonly used units: kilowatt (KW), milliwatt (mW)

1 kW = 103 W

1 W = 103mW

3. Definition: The ratio of electrical power to time is called electrical power

It is numerically equal to the electrical energy consumed by electrical appliances per unit time.

2. The origin of “kilowatt-hour”

If the units of P and t are kW and h respectively, then after multiplying them, we get another unit of electrical energy: kilowatt-hour (degree).

1 kilowatt hour can be regarded as the electrical energy consumed by an electrical appliance with a power of 1 kW for 1 hour.

1 degree=1 kW·h = 1×103 W×3 600 s = 3.6×106 J

Note: kW · h and kW are units of two different physical quantities.

Kilowatt hour is the unit of electrical work and energy, while kilowatt and watt are the units of electrical power.

The difference and connection between electric power and electric power.

Electrical work refers to the work done by the current, and it can also indicate the amount of electrical energy consumed in the circuit.

Electrical power is equal to the ratio of electrical work to the time used, and is a physical quantity that indicates how quickly electrical energy is consumed.

3. Rated voltage and rated power

Rated voltage: The voltage at which an electrical appliance operates normally. "U amount"

Rated power: The power of an electrical appliance at rated voltage. "P amount"

Xiao Ming bought an incandescent lamp from the mall and looked carefully at its nameplate. It said "PZ220,25" on it. What does it mean?

Pz means general lighting, 220v is its rated voltage, 25W is its rated power

Actual voltage, actual power

Actual voltage: the voltage when the electrical appliance is actually working, "Ureal"

Actual power: the power of electrical appliances under actual voltage, "P real"

Summary: Electrical appliances can only work properly if they are used at rated voltage. The actual voltage is low, the power consumed by the electrical appliance is low, and it cannot work properly. The actual voltage is too high. Long-term use will affect the life of electrical appliances and may even burn out the electrical appliances.

practise

1. Regarding electric power, which of the following statements is correct ( )

A. The more electrical energy consumed by an electrical appliance, the greater the power.

B. The shorter the time the electrical energy is consumed by the electrical appliance, the greater the power.

C. The more electrical energy consumed by an electrical appliance, the longer it is used, and the greater the power.

D. At the same time, the more electrical energy consumed by an electrical appliance, the greater the power.

2. Xiao Ming studied in the evening and used a "220 40W" light bulb to work for 3 hours. The electric energy consumed in the circuit is ____kW·h. If there is a "600revs/kW·h" electric energy meter connected to the circuit, then in this paragraph The turntable of the electric energy meter rotates ____ times during the time.

3. There are three incandescent lamps. A is marked with "PZ220-15", B is marked with "PZ220-40", and C is marked with "PZ220-100". When they are connected to the household circuit, the lighting conditions during normal operation are ( )

A.Light A is the brightest B.Light B is the brightest

C. The C light is the brightest D. The same light

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

The reporter's statement confused the concepts of electrical energy and electrical power.

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: 2024-07-06

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