"Causes of Excessive Current in Household Circuits" Daily Electricity PPT Download

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"Causes of Excessive Current in Household Circuits" Daily Electricity PPT Download

Part One: Knowledge Management

1. Causes of excessive current in household circuits: (1) The total power of household appliances is too large (overload); (2) Short circuit occurs.

2. The impact of the total power of household appliances on household circuits: According to the I=PU analysis, when the voltage remains unchanged, the power of household appliances increases, and the current in the circuit increases.

3. Effects of short circuits on household circuits

Short circuit: A short circuit in a household circuit means that the live wire and the neutral wire in the household circuit are directly connected with wires.

Impact: At this time, the resistance in the circuit is very small. When the voltage remains unchanged, according to the analysis of I=UR, the current in the circuit is very large.

Note: Short circuit and excessive total power of household appliances will cause excessive current in household circuits. According to Joule's law, excessive heat generated on wires will damage transmission lines, energy meters, and even cause fires.

PPT on the causes of excessive current in household circuits, part 2: classification and exploration

Type One: Causes of excessive total power of household appliances and its impact on household circuits

[2017 • Weihai, Shandong Province Note: Do not use high-power electrical appliances at the same time.

[Method Summary] There are only two reasons for excessive current in household circuits: one is that the total power of electrical appliances is too large, and the other is that a short circuit occurs. When encountering such a problem, you must find out what is causing it and analyze it based on the specific circuit.

Type 2: The impact of short circuit on household circuits

[2017•Wugang, Hunan]Many major fires in recent years have been caused by line failures. One reason is poor contact at the connections. At this time, compared with the well-connected circuit, the resistance value there increases (select "increase", "decrease" or "unchanged"), the electrical power consumed there will become larger, and local overheating will occur. Fires may occur; another reason is that the lines are severely aged, short circuits are prone to occur between the wires when the power is on, and the current in the wires is too large, causing fires.

[Analysis] When the line connection is in poor contact, the resistance there will increase compared with a well-connected circuit. According to the formula P = I2R, the electrical power consumed there will increase; another reason is that the line is seriously Aging, short circuits easily occur between wires when electricity is applied, and the resistance is 0. According to Ohm's law, the current in the wires is too large.

PPT on the causes of excessive current in household circuits, part three: evaluation in class

1. [2017•Guangzhou, Guangdong]In a certain household circuit, a fuse that meets the requirements is connected. When the switch is closed, the light does not light up but the fuse blows immediately. The reason for this phenomenon may be (B )

A. There is a break somewhere in the circuit

B． Connect one end of the switch to the neutral wire and the other to the live wire.

C. Connect the switch to the neutral line

D. The voltage in the circuit is too low

2. [2018•Wuzhou, Guangxi]If the air switch of Xiaoyu’s house tripped, it must be in the circuit (　D)

A. A circuit break occurred

B． Electrical resistance is too high

C. Voltage higher than 220 V

D. The total current is too large

3. [2018•Shandong Zaozhuang]In life, we sometimes encounter the following situations. In the following situations, what may cause the air switch in the household circuit to trip is (　A　)

(1) Add high-power electrical appliances to the circuit

(2) The two wire ends in the socket collide

(3) The two wire ends in the switch collide

(4) The insulation of outdoor transmission lines is damaged

A. (1) and (2) B. (2) and (3)

C. (1) and (3) D. (2) and (4)

[Analysis] (1) The addition of high-power electrical appliances to the circuit will cause the total power of the electrical appliances to be too large, resulting in excessive current, causing the air switch in the household circuit to trip; (2) two wires in the socket collide, It will cause a short circuit in the circuit, resulting in excessive current, causing the air switch in the household circuit to trip; (3) The two wires in the switch will collide, which will cause the switch to be unable to control the electrical appliances. The electrical appliances will continue to work, but will not cause the current to flow. If it is too large, it will not cause the air switch in the household circuit to trip; (4) The insulation of the outdoor transmission line is damaged, it will not cause the current in the household circuit to be too large, and it will not cause the air switch in the household circuit to trip. It can be seen that the factors that may cause the air switch in the household circuit to trip are (1) and (2), so choose A.

4. [2018•Jieyang, Guangdong]As shown in the figure, in the two circuits A and B, after the switch is closed, the transmission line burns due to excessive current. The reason for the excessive current in A is the total power Too large. The reason why B generates excessive current is a short circuit in the circuit.

PPT on the causes of excessive current in household circuits, part 4: layered operations

1. [2018•Tianjin Nankai District]The fuse in the home circuit has blown. Which of the following reasons is impossible (C)

A. The total power of the electrical appliances used is too high

B． The ends of two wires in the socket are touching

C. The ends of the two wires in the pull switch are touching.

D. The specifications of the fuse do not meet the specified requirements

2. [2018•Bengbu, Anhui]As shown in the picture, the insulation of the wire connecting the light bulb is damaged somewhere and collides with each other. At this time, the light bulb will (　D　)

A. Burned out B. become brighter

C. Normal light d. Can't shine

3. [2018•Tianjin]The air switch installed on the main road in Xiaoming’s home suddenly tripped. The reason must be (　A)

A. The current in the circuit is too large

B． There is a short circuit in the circuit

C. The voltage across the circuit is greater than 220 V

D. The total power of electrical appliances in the circuit is too large

4. [2017•Beijing Dongcheng]Air switch, also known as air circuit breaker, plays a timely protective role when short circuit or overload occurs in circuits or electrical equipment. When several electrical appliances are turned on and work at the same time for a period of time, the air switch trips; then it is closed, and then it trips again after working for a period of time. The reason for the above phenomenon is that the total power of the electrical appliances is too large (optional "The total power of the electrical appliances is too large" ” or “short circuit”).

5. [2018•Jiangsu Yancheng]As shown in the picture is Xiao Ming's experimental circuit diagram of "exploring the cause of the fuse blowing". Xiao Ming connected a wire between B and D. The switch was closed and the fuse was blown. Which of the following statements is correct (D)

A． When the fuse blows, the bulb will burn out

B． When the fuse blows, the current in the fuse is greater than the current in wire AB

C. If the wire is not connected between B and D but connected between A and C, the fuse will blow.

D. If there is no wire between B and D, and a light bulb is used instead of the wire between AB to connect to the circuit, the fuse will not blow.

6． [2018•Wuxi, Jiangsu]To explore the reason for the blown fuse, Xiao Ming connected the circuit as shown in the picture.

(1) The fuse is made of material with a lower melting point (please fill in "high" or "low").

(2) Turn on the power supply and close the switches of each small bulb branch in turn. You can see that the ammeter indication gradually increases (select "gradually increase", "gradually decrease" or "remain unchanged"). When the switch of the electric furnace wire branch is closed, it is found that the fuse is not blown. Next, a thicker electric furnace wire (select "thin" or "thick") should be used to continue the experiment.

Keywords: Free download of PPT courseware for ninth-grade physics from the People's Education Press, PPT download of causes of excessive current in household circuits, PPT download of daily electricity consumption, .PPT format;

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Update Time: 2024-10-03

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