"Electric Power" PPT Courseware 3

Description

"Electric Power" PPT Courseware 3

1. Exchange and research

Session 1. Inquiry between mentors and friends

1. Feedback before class preview:

Over a period of time, do the aluminum disks on the electricity meters of the neighbors rotate the same number of times, or do the aluminum disks rotate at the same speed?

Thinking: What does the speed of the aluminum disk on the electric energy meter relate to?

Demonstration experiment

Think independently first, then communicate with mentors and friends

Observation: Connect a 100W light bulb and an 800W hair dryer to the circuit respectively, and compare the rotation speed of the aluminum plate of the electric energy meter.

Thinking: If the aluminum disk on the electric energy meter rotates more times, it means that the current does ____ work, and if the aluminum disk rotates faster, it means that the current does _____ work. Therefore, when different electrical appliances work, the current does _______ work differently.

In physics, electrical power is used to express how quickly an electric current does work.

Session 2: Teacher’s instructions

1. Electrical power is a physical quantity that represents the amount of work done by a current, rather than the amount of work done. The greater the electrical power of an electrical appliance, the faster it consumes electrical energy.

2. Only when the time is fixed, electrical appliances with greater electric power consume more electric energy.

Judgment: The electric power of the air conditioner is 1000W and the electric power of the TV is 100W. Then the air conditioner must consume more power than the TV ( )

Think independently first, then learn from fellow students and give comments from the master.

1. The units of electrical energy and electrical power are ( )

A.Kilowatt hours and joules B.Watts and kilowatts

C. Joules and watts D. Kilowatts and kilowatt hours

2. For the following statement about electric power, the correct one is ( ) indefinite

A. Electric power is a physical quantity that indicates how much electrical energy an electrical appliance consumes.

B. The greater the electrical power of the electrical appliance, the faster the current will do work.

C. Electrical appliances with large electric power must consume a lot of electric energy when working.

D. Within a certain period of time, electrical appliances with high electric power consume more electric energy.

3. How long can a 40 W light bulb operate with 1 kWh of electricity?

Solution: P=40W=0.04KW t=1KW.h

2. Consolidate practice

1. Electrical power represents the physical quantity of how quickly electric current does work. The greater the electrical power of an electrical appliance, the faster the current does work and the faster it consumes electrical energy.

2. For formula calculations, pay attention to the uniform conversion of units.

3. Mutual assistance and improvement

Want to discuss

In life, which one is brighter, a 40W light bulb or a 100W light bulb?

A high-power light bulb looks brighter. Think about it: Does the same electrical appliance always have the same power under different voltages?

Demonstration experiment

Equipment: a small light bulb marked "2.5V 1.2W", power supply, sliding rheostat, voltmeter, wires, switch

Steps: Adjust the sliding rheostat so that the actual voltage of the bulb is 1.5V, 2.5V, and 2.8V respectively.

Phenomenon: Observe the brightness change of the light bulb.

in conclusion:

1. The electrical power of electrical appliances is _____ constant

2. The actual electrical power consumed by electrical appliances changes with ________.

3. The brightness of the light bulb depends on the size of _________

5. Test feedback

1. Judgment

(1) The faster an electrical appliance consumes electrical energy, the greater its electrical power. ( )

(2) High-power electrical appliances must consume a lot of electricity. ( )

2. Multiple choice questions

(1) Mom asked Xiao Ming to buy a 15W light bulb, where "15W" refers to the small light bulb ( )

A. Rated power B. Actual power C. Rated voltage D. Actual voltage

(2) Xiao Ming turns on the light at home. The brightness of the light at this time depends on ( )

A. Actual power of the lamp B. Current of the lamp C. Supply voltage D. Rated power of the lamp

(3) The rated voltage of a small light bulb is 1.5V, and the normal operating current is 0.3A, then the electric power is ( )

A. 0.45W B.5W C.0.2W D.4.5W

3 calculation

(1) How much energy does a hair dryer with a power of 800W consume when operating normally for 5 minutes?

(2) The rated power of the motor in the learning tool is 1.5W. When the circuit voltage is 3V, it works normally. What is the current of the small motor at this time?

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: 2024-10-18

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