"Electric Energy Electric Power" Electric Power PPT

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"Electric Energy Electric Power" Electric Power PPT

Part One: Guidance Design

Learning point 1 Electric energy and its units

Experiment 1: As shown in Figure 18-1-3, connect the circuit, close the switch, make the small light bulb shine, and explore the energy source of the light bulb.

Experiment 2: As shown in Figure 18-1-4, connect the hair dryer to a 220 V circuit, close the switch of the hair dryer, and make it work with the cold wind shield and the hot wind shield to explore the conversion of electric energy. .

Question 1: Battery is a common device for obtaining electrical energy. What is its energy conversion?

[Answer] When the battery supplies power to the outside world, it converts the stored chemical energy into electrical energy.

Question 2: How is energy converted when the hair dryer works?

[Answer] When the hair dryer works, it consumes electrical energy and converts it into mechanical energy and internal energy.

Question 3: Electric energy is a kind of energy. Its international unit is __________ with the symbol ____. The common unit is "kilowatt-hour" with the symbol ______, which is what we call ______ in our daily life. The conversion relationship is 1 kW·h=__________J.

Learning Point 2: Measurement of Electric Energy

Question 1: The electric energy consumed by electrical appliances over a period of time can be measured by ________.

Question 2: The calibrated current of Xiao Ming’s electric energy meter is ____A, and the maximum current in a short period of time must not exceed _____A.

Question 3: The electricity consumed by Xiao Ming’s home this month is _______kW·h, which is equal to ____________J.

Question 4: For every electrical appliance connected to the electric energy meter that consumes 1 kW·h of electric energy, the turntable on the electric energy meter rotates 3000 times, so the electric energy consumed when it rotates 1 rotation is ________kW·h, which equals ____________J ; If it is observed that the electric energy meter rotates 8 times in 3 minutes, then the power consumed in 3 minutes is __________J.

Learning Point 3: Electrical Power

Materials: Figure 18-1-6 shows the schematic diagram of a hydroelectric power station.

Question 1: Does the water flow do work on the turbine?

Question 2: The water flow can do work on the turbine, but does the current do work?

Question 3: There are various forms of expression of work done by electric current. Work is done when electric current passes through the motor to lift the heavy object. So when the current passes through the lamp, it emits light, and when the current passes through the electric furnace, it generates heat. Does this count as work?

[Answer] Here, we should expand the concept of "work": using a motor to move an object is a manifestation of the work done by the current. Electrical current uses electrical appliances to generate heat and light, which is another manifestation of the work done by electric current. In short, there are many phenomena of current doing work. Any change caused by current is a manifestation of current doing work.

Question 4: Write down the conversion of energy in the following scenarios: (1) the motor rotates; (2) the fluorescent lamp emits light; (3) an electric kettle is used to boil water.

[Answer] (1) Electrical energy → mechanical energy; (2) Electrical energy → Light energy; (3) Electrical energy → Internal energy.

Question 5: What is the essence of work done by electric current?

[Answer] The essence of work done by electric current is the conversion of electrical energy into other forms of energy. How much work is done by the current, how much electrical energy is converted into other forms of energy.

Learning point 4: Calculation of electrical power

Explore: What factors are related to the work done by electric current.

Experiment 1: Connect two different motors in series in the same circuit to lift a heavy object, compare the height of the two motors lifting the same heavy object at the same time, and compare the relationship between the work done by the current and the voltage.

Experiment 2: Connect two different motors in parallel in the same circuit to lift a heavy object, compare the height of the two motors lifting the same heavy object in the same time, and compare the relationship between the work done by the current and the current.

Electric energy and power PPT, part 2: application examples

Type 1 Electric energy

Example 1 Among the household appliances shown in Figure 18-1-3, the ones that mainly convert electrical energy into internal energy are ()

[Error-prone warning] ①The process of converting electrical energy into other forms of energy is the process of current doing work. How much electrical energy is converted is said to be how much work (electrical work) is done by the current. In daily life, we often talk about how much electrical energy is consumed, but generally do not talk about how much work the current does. In fact, the two statements are equivalent.

② Judgment on the conversion of electrical energy: Generally, what moves after electricity is turned on is the conversion of electrical energy into mechanical energy, and what produces heat after electricity is turned on is the conversion of electrical energy into internal energy.

Type 2: Measurement of electrical energy

Example 2 2018•Shiyan Adaptation The reading on Xiaotianjia’s electric energy meter at the beginning of this month is , and the reading at the end of this month is shown in Figure 18-1-4. The electricity consumed by Xiaotianjia this month is ________kW·h. If the turntable of the electric energy meter rotates 300 times in 10 minutes, the electric energy consumed by the electrical appliance connected to the electric energy meter during these 10 minutes is ________kW·h.

[Method guidance]The "degree" and "number of revolutions" of the electric energy meter

(1) "Degree" is the common name for the commonly used unit of electric energy meters, kilowatt-hour (kW·h). Its conversion relationship with the international unit of electric energy, joule (J), is: 1 kW·h=1 kW×1 h=1000 W× 3600 s=3.6×106 J.

(2) Use the electric energy meter constant N imp/(kW·h) or N r/(kW·h) and the number of flashes n of the electric energy meter indicator light or the number of turns n of the turntable within a period of time to calculate the energy consumption during the period. The method of electrical appliances consuming electric energy W: W=n impN imp/(kW·h)=nN kW·h or W=n rN r/(kW·h)=nN kW·h.

Type 3 Electric Power

Example 3 As shown in Figure 18-1-5, R1 and R2 are connected in series in the circuit, R1 = 6 Ω, R2 = 9 Ω, and the voltage across the resistor R2 is 9 V. ask:

(1) How much work does the current pass through R1 in 1 minute?

(2) How much work does the current pass through R2 in 1 minute?

(3) What is the total work done by the current?

[Method guidance]Calculation of electrical power

(1) Understanding of the electric power formula W=UIt

①Simultaneity: Corresponding to the current and voltage at the same period of time.

② Homogeneity: Current and voltage should correspond to the same conductor in the circuit.

③Unit correspondence: U-V, I-A, t-s⇒W-J.

(2) Two methods for solving the electric energy consumed by the entire circuit (current work)

Electric energy and power PPT, part 3 content: classroom feedback

1. Among the following electrical appliances, the ones that mainly convert electrical energy into mechanical energy during operation are ()

A． Soldering iron b. Electric fan C. Electric iron D. electric kettle

2. Regarding the parameters of electric energy shown in Figure 1-1, which of the following statements is incorrect ()

A． For every 1 kW·h of electricity consumed, the energy meter's turntable rotates 2500 times.

B． This energy meter is used in a 50 Hz AC circuit

C. The unit of energy meter reading is kW·h

D. When the energy meter is working normally, the voltage must be 220 V and the current must be 5 A.

3. The reading on the electric energy meter at Xiao Ming’s home at the beginning of a certain month is shown in Figure 18-1-8A, and the reading at the end of the month is shown in Figure B. Then the electricity consumed by Xiao Ming’s home in that month is ________kW·h, which is _ ___________J.

4. The amount of work done by the current is related to ______________, ______________, and ______________. Calculation formula: ________. Where W represents ________, the unit is ________; U represents ________, the unit is ________; I represents ________, the unit is ________; t represents ________, the unit is ________.

5. Two dry batteries are connected in series to power the small bulb. The voltage is 3 V. The current passing through the small bulb when it emits light is 0.3 A. At this time, the resistance of the small bulb is ________Ω, and the power consumed by working for 30 s is _________J.

6． A power supply with a constant voltage of 3 V is used to power a small motor to rotate. The power consumed by the small motor in 1 minute is 36 J, and the current through the motor is ________A.

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Update Time: 2024-10-21

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