"How to use electricity safely" PPT courseware on household circuits and safe electricity use

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"How to use electricity safely" PPT courseware on household circuits and safe electricity use

Electricity is a "toothless tiger"

Have you experienced or heard of any accidents caused by carelessness in using electricity? Please give an example!

For example: tripping caused by overload

Short circuit causes fire

Casualties caused by electric shock

1. Prevent overloading

Total current in main circuit:

I total = I1 +I2 + I3 + I4

=0.75A+0.75A+0.75A+0.75A

=3A

The total current in the main circuit is greater than the maximum current that the fuse can withstand 2.5A

The current passing through the circuit is too large, which generates a lot of heat and causes the fuse to melt.

2. Never short circuit

According to Ohm's law I=U/R, when the voltage in the circuit remains constant, because the resistance of the circuit without electrical appliances is very small, the current in the circuit is surprisingly large and a lot of heat is generated.

The phenomenon that the live wire is in direct contact with the neutral wire without using electrical appliances - short circuit

What are the dangers of short circuit?

A short circuit in the circuit will burn out the wires and power supply, and may also easily cause a fire.

What measures are taken to prevent short circuits?

A fuse must be connected to the circuit

Reasons for blown fuse

Household fuses are made of a lead-antimony alloy with a relatively _____ resistivity and a relatively _____ melting point.

When too much current passes through the fuse, the fuse produces more __________, causing its temperature to reach _____,

Fuse _____, automatically cuts off the circuit and plays the role of insurance __________.

The fuse should be installed on _____ road.

3. Avoid electric shock

Electric shock refers to an injury accident caused when current passes through the human body to a certain extent. The human body is a conductor. When the human body touches a charged object, current flows through the human body, which is an electric shock.

Electric shocks in household circuits are caused when a human body that is not insulated from the ground directly or indirectly touches a live wire, causing current to pass through the human body - electric shock.

2. What factors are related to the danger of electric current to the human body?

The size of the current, the length of time it is energized, the parts of the human body where the current passes, etc.

From I=U/R, the current passing through the human body depends on

Applied voltage and the body's own resistance

a. The resistance of the human body is not necessarily the same for different people.

b. The resistance of the same person is greater when the skin is dry and smaller when the skin is moist.

Principles of safe use of electricity

1. The installation of electrical equipment must meet technical requirements.

2. Do not come into contact with charged objects higher than 36V.

3. Keep away from high-voltage charged objects.

4. Do not use electrical appliances when they get wet.

5.Do not damage the insulators in electrical equipment.

First aid for electric shock

1. First, cut off the power supply, or use a dry wooden stick to spread the wires, and quickly remove the person who was electrocuted from the power source (never touch the person who was electrocuted directly).

2. If the person is seriously electrocuted, artificial respiration is required.

3. Send to hospital.

4. When a fire occurs, the power supply must be cut off first to carry out fire-fighting operations.

Summary of safe electricity use

1. The voltage that is safe for human body use is: no higher than 36V.

2. Forms of electric shock:

1 "Low voltage electric shock": single line electric shock, double line electric shock

2 "High-voltage electric shock": arc electric shock, step voltage electric shock

3. Principles for safe use of electricity: Do not come into contact with low-voltage charged objects, and do not approach high-voltage charged objects.

4. First aid methods for electric shock

(Turn off the power, use a dry wooden stick to remove it, and perform artificial respiration)

How to avoid electric shock from home circuits

1. The switch must be connected to the live wire.

2. When installing the screw lamp holder, connect the live wire to the middle copper piece and the neutral wire to the spiral.

3. Do not let indoor wires come into contact with other metal conductors, and do not dry clothes or hang items on wires. When wires are aged or damaged, they must be repaired in time.

4. The place where electrical appliances should be grounded must be grounded as required.

5. No need to wet hands to turn switches, change light bulbs, plug in or pull out plugs.

6. Do not stand on wet tables and chairs to touch the live wire.

7. Before touching the wire, turn on the main switch. If you have to operate it with power on, be sure to insulate it from the ground. Use a test pen to check whether the contact point is connected to the live wire, and operate it with one hand as much as possible.

Class summary

When using household circuits, be sure to prevent overloading and avoid short circuits. Install electrical appliances in accordance with the technical requirements stipulated by the state to avoid electric shock.

I hope that students will pay more attention to electricity safety in their daily lives and actively promote electricity knowledge to those around them!

Classroom training

1. (2011 Guangzhou, Guangdong) In the circuit shown in the picture, all three lights that were glowing normally suddenly went out. After checking that the fuse was intact, a test pen was inserted into the two holes of the socket, and the neon tubes all glowed. The reason for this phenomenon is ( )

A. The socket is short-circuited

B． The fire line entering the house is cut off

C. The zero line entering the house is broken

D． The filament of a certain electric lamp is broken

2. (2011 Lianyungang, Jiangsu) Among the practices reflected in the following four figures, the ones that are in line with electricity safety are ( )

A. Connection of switch and light bulb B. Use of test pen

C. The TV antenna is in contact with the wire D. Wet hand contact switch

3. (2011 Guang'an, Sichuan) As shown in the picture, please connect the following components to form a household circuit that meets the requirements for safe electricity use.

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For more information about the PPT courseware "Household Circuits and Safe Use of Electricity, How to Use Electricity Safely", please click the "Household Circuits and Safe Use of Electricity ppt How to Use Electricity Safely" ppt tag.

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Update Time: 2024-06-25

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 2 industry PPT template

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