"Electric Power" Electric Power PPT Courseware 2

Description

"Electric Power" Electric Power PPT Courseware 2

Knowledge review

(1) What is electric power? What letters are used?

The work done by current is called electrical work and is represented by the letter W

(2) What are the two units of electrical power? What's the conversion relationship?

The unit of electrical power is Joule, represented by the letter J

Kilowatt hour (degree), represented by the letters KW·h

The conversion relationship is: 1 KW·h=3.6×106J

(3) What is the essence of electric power? What instrument is used to measure electrical power?

The process of current doing work is essentially the process of converting electrical energy into other forms of energy.

How many joules of work are done by the current, how many joules of electrical energy are converted into other forms of energy.

Measuring electrical power with an energy meter

think

(1) After the light bulb shines for a period of time, how do you feel when you touch the light bulb with your hand? Why?

(2) After using the electric fan for a period of time, how does it feel when you touch the motor part with your hands? Why?

Answer: Hot. It is the heating effect of electric current.

analyze:

Under the same conditions of energizing current and energizing time, the greater the resistance, the more heat generated by the current.

Under the same conditions of resistance and energization time, the greater the current, the more heat the current generates.

Further research showed that the heat generated is proportional to the square of the current.

Under the same conditions of energizing current and resistance, the longer the energizing time, the more heat generated by the current.

The British physicist Joule summarized Joule's law through a large number of experiments.

1. Content: The heat generated by current passing through a conductor is proportional to the square of the current, proportional to the resistance of the conductor, and proportional to the energization time.

2.Formula: Q = I²Rt

3. Unit: I-ampere, R-ohm, t-second, Q-joule.

According to Ohm's law and Joule's law, derive the electric work formula

If all the work done by the current is used to generate heat, W = Q

And ∵Q = I²R t

According to Ohm's law U = IR

∴ W = Q = I²Rt = IR I t =UIt

W=UIt is applicable to the work done by the current under any circumstances, while Joule's law Q=I²R t is applicable to the heat calculation of any electrical appliance. Q=W=UIt can also be used to calculate the heat of a circuit where there is only the thermal effect of the current.

Discuss based on what you have learned

Through exploration, complete the following questions: (if R1>R2)

1. How to connect two resistance wires? ( )

2. What is the relationship between the currents between the two? ( )

3. Which resistance wire has a higher voltage across it ( )

4. Which resistance wire causes the temperature of kerosene to rise faster? ( )

5. In the same period of time, which resistance wire consumes more power ( )

in conclusion:

When the current flowing through the electrical appliance and the power-on time are the same, the higher the voltage on the electrical appliance, the more work the current does. "

practice

1. There is an electrical appliance in the circuit. The voltage at both ends is 6V. The current passing through it is 200mA. What is the work done by the current in 5 minutes?

2. When two resistors with resistance values ​​of 4Ω and 6Ω are connected in parallel on a 4V circuit and are powered for 1 minute, how much work is done by the current passing through each resistor? When they are connected in series on a 4V circuit and powered for 1 minute, How much work is done by the current flowing through each resistor?

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For more information about the "Electric Power and Electric Power" PPT courseware, please click on the Electric Power ppt Electric Power ppt tab.

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Update Time: 2024-10-20

This template belongs to Physics courseware Lu Jiao Edition Ninth Grade Physics Volume 1 industry PPT template

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