"Household Circuit" Electric Power and Electric Power PPT Courseware 3

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"Household Circuit" Electric Power and Electric Power PPT Courseware 3

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Composition: Generally consists of entrance wire, ________, main switch, protection equipment, electrical appliances and wires, etc.

One of the entrance lines is ________ and the other is the neutral line. Under normal circumstances, there is a voltage of 220 V between the live wire and the neutral wire

Electric energy meter is an instrument that measures how much electricity a user consumes

Connection of various components All electrical appliances and sockets in the household circuit are connected in parallel in the circuit. Each lamp has its own control switch. The switch is connected between the live wire and the lamp and is connected to the lamp _____

Fuse

Composition Made of lead-antimony alloy with relatively high resistance and low melting point

Function: When the current in the circuit is too large, the fuse will melt quickly due to heat, automatically cutting off the circuit and functioning as a ____ circuit

Choose so that its rated current is equal to or slightly greater than the maximum normal operating current of the circuit

Causes of excessive current in household circuits

A short circuit occurs and the power of the electrical appliance is too high

How to understand the function of fuse

Fuse is commonly known as fuse, which uses the heating effect of current to work. To avoid accidents when the current is too large, fuses must be installed in household circuits.

(1) Material: The fuse is made of lead-antimony alloy with relatively high resistance and low melting point.

(2) Principle: The fuse is usually connected in series on the live wire. When the current in the circuit is too large, the resistance of the fuse is relatively large. According to P=I2R, the fuse will generate more heat, causing its temperature to reach the melting point. , so the fuse blows, automatically cutting off the circuit and playing a role in protecting the circuit.

(3) Selection: The fuse should be selected according to the maximum current specified by the wire. If the fuse selected is too thick and its rated current is too large, then when the current in the circuit is too large, the fuse will not blow and it will not be able to protect the circuit. If the fuse selected is too thin and its rated current is small, the fuse will have blown before the current in the circuit reaches a dangerous level, which will cause trouble for household electricity. When the fuse is blown, you should first find out the cause of the burnout, eliminate the fault, and then replace it with a fuse of appropriate specifications as required. Do not use ordinary copper wire or iron wire as a fuse. Because copper wire and iron wire have high melting points, they cannot provide protection and may cause major accidents. You should not intentionally cause a short circuit to test whether the fuse will blow. This is absolutely not allowed.

[Example] When a fuse is installed in a household circuit (a fuse is installed, commonly known as a "fuse"), its function is ()

A. Automatically cut off the circuit when the voltage is too high

B. Automatically cut off the circuit when an electric shock occurs

C. Automatically cut off the circuit when electrical leakage occurs

D. Automatically cut off the circuit when the current in the circuit is too large

Analysis: The fuse uses the heating effect of current to work. The fuse is usually connected in series on the live wire. When the current in the circuit is too large, because the resistance of the fuse is relatively large, according to P=I2R, the fuse will generate more heat, causing its temperature to reach the melting point, and the fuse will blow. , automatically cuts off the circuit and plays a protective role. There are two reasons for a blown fuse in a household circuit: first, the total power of the electrical appliances in the circuit is too large, and second, a short circuit occurs in the circuit. If the voltage at both ends of the circuit is too high and an electric shock occurs or an electrical appliance leaks, as long as the current in the circuit is not too large, enough heat will not be generated at the fuse and the fuse will not blow automatically, so items A, B, and C None of them are correct, the correct option is D.

1. In household circuits, the correct connection sequence from the entrance line is ()

A. Knife switch, energy meter, fuse box, socket

B. Knife switch, energy meter, socket, fuse box

C. Electric energy meter, fuse box, knife switch, socket

D. Electric energy meter, knife switch, fuse box, socket

2. Which of the following statements about home circuits is correct ()

A. The voltage of household circuit is 380 V

B. Electrical appliances in household circuits are all connected in series

C. The blown fuse is caused by the total power of the circuit being too large.

D. There must be a series relationship between the switch and the bulb

3. The fuse in the household circuit is broken. Regarding the replacement of the fuse, which of the following statements is correct ()

A. Use iron wire or aluminum wire instead

B. For insurance, choose a fuse as thick as possible

C. Choose a fuse with a rated current equal to or slightly larger than the maximum normal operating current in the circuit.

D. Choose a fuse with a rated current equal to or slightly smaller than the maximum normal operating current in the circuit.

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For more information about the "Household Circuit Electrical Work and Electrical Power" PPT courseware, please click on the "Household Circuit ppt Electrical Work and Electrical Power ppt" tab.

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Update Time: 2024-07-01

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