"Scientific Exploration: Thermal Effect of Current" Current Work and Electric Power PPT Courseware 3

Description

"Scientific Exploration: Thermal Effect of Current" Current Work and Electric Power PPT Courseware 3

physics in life

Last Saturday, the mother of Xiaowei's classmate from our school told him to do his homework and not watch TV before going out. When his mother came back, she was very happy to see him doing his homework seriously without turning on the TV. But when he touched the back cover of the TV with his hand, he discovered that Xiaowei had just watched TV.

Do you know what Xiaowei’s mother based her judgment on?

In life, many electrical appliances are accompanied by heat when they are connected to the power supply.

1. Thermal effect of electric current

In life, many electrical appliances are accompanied by heat when they are connected to the power supply.

What characteristics do the above electrical appliances commonly used in daily life have in common?

When electric current passes through a conductor, electrical energy is converted into heat energy. This phenomenon is called the thermal effect of electric current.

2. Explore: What factors are related to the thermal effect of electric current?

The electric furnace wire is connected to the circuit through a wire, and the current passing through the electric furnace wire and the wire is the same. Why is the electric stove wire so hot that it glows red, but the wire barely heats up?

[Conjectures and Assumptions]

1. It may be related to resistance

2. It may be related to current

3. It may be related to the power-on time

[Experiment 1] Explore the relationship between electric heating and resistance

Constant physical quantities should be controlled: the same current and power-on time

Physical quantity that should change: resistance

How can I make two different resistors have equal current and energization time?

concatenate them

3. Joule’s Law

Joule's Law: The heat generated by an electric current passing through a conductor is proportional to the square of the current, the resistance of the conductor, and the time it is energized.

Formula: Q = I²Rt

Meaning: Heat Current Resistance Time

Unit:JAΩS

Theoretical derivation of Joule's law

When a current passes through a conductor, if all the electrical energy consumed is converted into heat without being converted into other forms of energy at the same time, then the heat Q generated by the current is equal to the electrical energy W consumed.

That is: Q = W = Pt = UIt = IR It = I2Rt

test you:

The current passing through the electric stove wire and the wire is the same.

Why do electric stove wires glow red when hot, but the wires barely heat at all?

Reason: The wire resistance is much smaller than the electric furnace wire resistance and generates less heat.

4. Utilization and prevention of electric heat

(1) Utilization of electric heat

Application of electric heating in daily life

(2) Dangers of electric heating

Burned out electrical appliances

Fire caused by aging wire insulation

(3) Prevention of electric heating

TV cooling window

summary

1. Thermal effect of electric current

Definition: The phenomenon that a conductor generates heat when electric current passes through it.

Essence: Electrical energy is converted into internal energy.

2. Electric heater

Definition: A device that converts electrical energy into internal energy.

Principle: Thermal effect of electric current.

Composition: The heating element is made of alloy with high resistivity and high melting point.

practice

1. The heating effect of electric current is the phenomenon that _____ is converted into ____ when electric current passes through a conductor. An electric heater is a heating device made of _______ that uses electric current.

2. In the experiment of "studying the relationship between the heat generated by electric current and the current", _____ and _____ should be kept constant, and a sliding rheostat is used to change the current of the resistance wire.

3. The current flowing through a 100Ω resistance wire is 2A, its electrical power is ___W, and the heat generated when it is powered for 1 minute is _______J.

4. Resistors R1 and R2 are connected in series in the circuit, R1=4, R2=6, then P1:P2=_____.Q1:Q2=______.

5. There are two electric furnaces A and B. It is known that the electric furnace resistance R1>R2 is connected to a circuit with a power supply voltage of 220V. Their heating conditions during the same time are ( )

A. A releases more heat. B. B releases more heat.

C. The same amount D. Unable to judge

6. Connect a "220V 100W" electric fan, a "220V 100W" charger, and a "220V 100W" electric soldering iron to the 220V power supply respectively. During the same time, the heating power generated when the current passes through them The biggest is ( )

A Soldering iron B Charger

C electric fans D as many

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For more information about the PPT courseware "Current Work and Electric Power Scientifically Exploring the Thermal Effect of Current", please click the "Current Work and Electric Power PPT Scientific Exploration of the Thermal Effect of Electric Current" ppt tag.

"Scientific Exploration: Thermal Effect of Current" Current Work and Electric Power PPT Courseware 2:

"Scientific Exploration: Thermal Effect of Current" Current Work and Electric Power PPT Courseware 2 Project Main Content Electric heater is a heating device made by utilizing the thermal effect of electric current. The main component of the electric heater is the heating element. The heating element is made of high resistivity and high melting point. Made of alloy..

"Scientific Exploration: Thermal Effect of Current" PPT courseware on current work and electric power:

"Scientific Exploration: Thermal Effect of Electric Current" PPT Courseware on Current Work and Electric Power Learning Objectives 1. Know the thermal effect of electric current and the working principle of electric heaters. 2. Understand the factors related to the heat generated by current. 3. Master the content, formula, and...

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Update Time: 2024-07-15

This template belongs to Physics courseware Shanghai Science Edition Ninth Grade Physics industry PPT template

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