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

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

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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 an alloy with high resistivity and high melting point.

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

Thermal effect

Joule's Law The heat generated by an electric current passing through a conductor is directly proportional to _______, directly proportional to the _______ of the conductor, and directly proportional to _______

Formulas and units Q=______, the international units are joules, amperes, ohms, seconds

A large number of experiments have shown that the heat generated when electric current passes through a conductor is related to the current of the conductor, the resistance of the conductor and the energization time. Joule's law quantitatively describes the thermal effect of electric current.

The formula Q=I2Rt is an experimental conclusion. As long as there is current passing through the conductor, it can be used to calculate the heat generated. When using the formula, pay attention to the conditions of the same section of conductor or the same circuit and the same time.

The derived formula Q=UIt=U²/Rt is only applicable to pure resistance circuits. In non-pure resistance circuits, the derived formula is not valid.

[Example] Xiaoyu and Xiaogang want to use the device as shown in the picture to explore "the relationship between the heat generated by a conductor and its resistance." Two identical flasks are filled with appropriate amounts of kerosene. A section of copper wire is soaked in flask A, which has a low resistance; a section of nickel-chromium alloy wire is soaked in flask B, which has a large resistance. The thermometer shows the temperature of kerosene.

In order to ensure that the experiment is scientific and reasonable, the mass of kerosene in the two flasks should be ______.

During the experiment, Xiaoyu and Xiaogang found that the thermometer in flask B increased rapidly, which showed that when the current and energization time are the same, the greater the resistance of the conductor, the more heat generated ______.

Analysis: The amount of heat generated by a conductor depends on the current, resistance and energization time of the conductor. In the experiment, the temperature increase of the same mass of kerosene is used to reflect the amount of heat generated by the conductor. When the current and energization time are the same, the conductor The temperature of the kerosene in flask B with high resistance rises quickly, which means that the greater the resistance of the conductor, the more heat is generated.

Knowledge point 1: Thermal effects and applications of electric current

1. Among the following electrical equipment, the one that mainly uses the thermal effect of current to work is ()

2. Which of the following situations does not belong to the prevention of electric heating hazards ()

A.The back cover of the TV has many holes

B. There is a small fan in the computer case

C. The motor housing has many heat sinks

D. If the appliance is not used for a long time, it should be powered on once in a while.

3. Regarding electric heating, which of the following statements is correct ()

A. Electric heat is harmful

B. The heating element of the electric heater is made of resistance wire with high melting point and high resistance.

C. Induction cookers, electric fans, and electric irons are all electric heaters

D. The greater the current passing through a conductor, the more heat is generated.

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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.

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Update Time: 2024-08-30

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

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