"Electric Power" Electric Power PPT

Description

"Electric Power" Electric Power PPT

Part One: Guidance Design

Learning point 1 Electric power

Experiment: Connect a 24 W energy-saving lamp and a 500 W hair dryer to the home circuit teaching board, and count the number of rotations of the energy meter turntable in 1 minute.

Question 1: In 1 minute, who is connected to the circuit and the energy meter turntable rotates the most times? Why does this happen?

Answer

Question 2: Do you know the physical meaning of 24 W and 500 W?

[Answer] 24 W and 500 W are the rated powers of these two electrical appliances.

Learning point 2: The origin of “kilowatt hour”

Question 1: What is the unit for measuring electrical energy in household circuits? What is its scientific name?

[Answer] Degrees Kilowatt-hours

Question 2: What is the physical meaning of 1 kilowatt hour of electricity?

Answer

Learning point 3: Measurement of rated power and electrical power

Explore: What are the factors that affect the brightness of incandescent lamps.

Experiment 1: Figure 18-2-3 shows the nameplates of two ordinary incandescent lamps. Let them work at a voltage of 220 V at the same time to compare their brightness.

Experiment 2: As shown in Figure 18-2-4, connect one of the light bulbs to both ends of the voltage regulator, and observe the change in brightness of the light bulb while adjusting the voltage.

Electric Power PPT, Part 2: Application Examples

Type 1 Electric power

Example 1 Regarding electrical power, which of the following statements is correct ()

A． The more electricity an appliance consumes, the greater its power

B． The shorter the time an electrical appliance consumes electricity, the greater the power

C. The more electricity an appliance consumes, the longer it is used, and the greater the power

D. In the same period of time, the more electrical energy consumed by an electrical appliance, the greater the power

[Analysis]The concept of electric power uses the ratio definition method, that is, electric power is equal to the ratio of electric power to time. Electrical appliances consume a lot of electric energy, but the electric power is not necessarily large. Electrical appliances consume electric energy for a short time, and the electric power is not necessarily large. Therefore, options A and B are incorrect. Electrical appliances consume a lot of electricity, take a long time, and do not necessarily have large electric power, so option C is incorrect. In the same period of time, the more electrical energy consumed by an electrical appliance, the greater the ratio of W to t, that is, the greater the electrical power, so option D is correct.

Type 2: Simple calculation of electrical power

Example 2 An electric furnace is connected to a lighting circuit and works for 10 s, and the current does 4840 J of work. beg:

(1) The electric power of this electric furnace.

(2) The electric energy consumed by the electric furnace for 30 minutes a day and a month (30 days).

Example 3 is shown in Figure 18-2-3, R1=24 Ω, R2=36 Ω, and the current in the circuit is 0.2 A. beg:

(1) Electric power of R1.

(2) Electric power of the entire circuit.

(3) The power consumed by the entire circuit when working for 3 minutes.

Type 3: Related calculations of rated power and actual power

Example 4: The nameplate of a soldering iron is marked with "220 V 110 W". If the soldering iron is connected to a 110 V circuit, the correct one of the following statements is (resistance remains unchanged) ()

A． The actual power of the soldering iron is 55 W

B． The actual power of the soldering iron is 27.5 W

C. The actual current flowing through the soldering iron is 20 A

D. The resistance of the soldering iron is 10 Ω

Electrical Power PPT, Part 3: Class Feedback A

1. In physics, electrical power is used to express the ________ of work done by an electric current. Its magnitude is equal to the ratio of ________ to ________. The unit of electrical power is ________. A high electric power means that the electric appliance consumes _________ electricity, and a small electric power means that the electric appliance consumes _________ electric energy.

2. Which of the following statements is correct ()

A． The more work the current does, the greater the electrical power

B． The longer the current does work, the greater the electrical power

C. The faster the current does work, the greater the electrical power

D. The greater the electrical power, the more work will be done by the appliance.

3. The electric power of a certain vacuum cleaner is 0.8 kW, which equals ________W, and its physical meaning is ____________________.

4. The electrical power of the two light bulbs is 50 W and 25 W respectively. They both consume 100 J of electric energy. The time used by the 50 W light bulb is ________, and the time used by the 25 W light bulb is ________. That is to say, the same electric energy is consumed. The time used by a high-power bulb is ________ (please fill in "long" or "short"), and the time used by a small-power bulb is ______ (please fill in "long" or "short"). Therefore, the electric power is A physical quantity that represents the work done by an electric current ________.

5. If the electrical energy consumed by a certain electrical appliance within 25 hours is 1 kW·h, then the electrical power of the electrical appliance is __________kW, which equals ________W.

6． As shown in Figure 2-1, the current in the flashlight is 0.5 A, and the power source is two new dry batteries, then the power of the small bulb of the flashlight is ________.

7． In the circuit shown in Figure 2-2, the power supply voltage is 3 V, the switch is closed, the voltage across the resistor R is 1 V, and the current in the circuit is 0.2 A. beg:

(1) Electric power of resistor R.

(2) The electrical power of light bulb L.

(3)The total power in the circuit.

Electrical Power PPT, Part 4: Class Feedback B

1. A light bulb marked with "36 V 40 W" has a rated voltage of ________V, a rated power of ________W, and the resistance of the light bulb during normal operation is ________Ω. When the light bulb is connected to a circuit and the voltage across the light bulb is measured to be 18 V, the actual power of the light bulb at this time is ________W. When the light bulb is connected to another circuit and the current through the light bulb is measured to be 1 A, the actual voltage across the light bulb is ________V and the actual power is ________W. (Ignore the effect of temperature on filament resistance)

2. What determines the brightness of the light bulb is ()

A． Current passing through the filament B. The resistance of the light bulb itself

C. The rated power of the light bulb D. The actual power of the light bulb

3. There are two electric lamps A and B, marked with "220 V 36 W" and "36 V 36 W" respectively. If they can both emit light normally, then ()

A． A light is on B. Light B is on C. As bright D. unconfirmed

4. A light bulb marked "12 V 6 W" is connected to the circuit and the measured current through it is 0.4 A. Then the actual power of the light bulb ()

A． Equal to 6 W B. Less than 6 W C. Greater than 6 W D. Unable to judge

5. Figure 2-3 shows the relationship between the current and the voltage of a small "6 V 1.5 W" light bulb. If these three light bulbs are connected in series and connected to both ends of the 12 V power supply, then At this time, the resistance of each bulb is ________Ω, and the actual power is ________W.

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Update Time: 2024-10-02

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