"Conductive Properties of Different Materials" Simple Circuit PPT Courseware

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"Conductive Properties of Different Materials" Simple Circuit PPT Courseware

1. Conductors, Insulators and Semiconductors

Observation and thinking

The inside of the wire is a metal wire, and the outside is covered with a layer of plastic or rubber. Do you know why?

Student experiment: Conductivity of different substances

You are given a ruler, a stick, an eraser, glass, and salt water. Which substances are easy to conduct electricity? Which substances are not easy to conduct electricity? How do you distinguish them?

In addition to testing substances, what other equipment is needed?

Power supply, wires, switches, ammeters, light bulbs, etc.

Small light bulb detection method, ammeter detection method

Experimental Results

Connect ________ and ________ into the circuit, and there will be current in the circuit. This shows that these objects are easy to conduct electricity, and we call them conductors.

When _______, ________ and ________ are connected to a circuit, there is no current in the circuit. This shows that these objects are not easy to conduct electricity, and we call them insulators.

Discussion

1. Conductor: An object that easily conducts electricity is called a conductor.

Examples: metal, graphite, human body, earth

Aqueous solutions of acids, bases, and salts

2. Insulator: Objects that do not conduct electricity easily are called insulators.

For example: rubber, glass, ceramics, plastics, oil

3. Semiconductor: A class of materials whose conductivity is between that of conductors and insulators is called a semiconductor.

Common semiconductor materials are germanium, silicon, gallium arsenide

Mainly used in the electronics industry

Science Window

1. The reason why conductors can conduct electricity easily: there are a large number of charges that can move freely in the conductor.

Knowledge of the composition of matter:

Matter -- molecules -- atoms -- nuclei electrons (high-speed motion)

2. In insulators, electric charges are almost all bound within the atoms and cannot move freely. There are very few free charges, so it is not easy to conduct electricity.

Think about it: Are the conductive properties of the same substance constant?

Experiments show that

There is no absolute boundary between conductors and insulators, and objects that are not conductive under normal circumstances may become conductive when conditions change.

think

In the experiment just now, when the voltage was the same and the circuit was connected to different conductors, would the ammeter readings be the same?

2. Resistance

(1) Significance: Resistance is a physical quantity that indicates the magnitude of the resistance of a conductor to electric current and is represented by the symbol R. Resistance is a property of the conductor itself.

(2) Unit: Ohm, abbreviated as ohm, represented by the symbol Ω.

1 kΩ=1000 Ω

1MΩ＝103 kΩ= 106 Ω

(3) The symbol in the circuit is

Typical Examples

Example: 1. Under normal circumstances, which of the following objects is a conductor? ( )

A. Glass rod B. Bicycle tire

C. Plastic rope D. Copper wire

analyze

Bicycle tires are made of rubber. Glass, plastic, and rubber are all insulators. Only copper is a conductor. Why do we need to add the condition of normal conditions to this question? Because there is no absolute boundary between conductors and insulators. When glass is heated to a very high temperature, it will become a conductor.

2. Why are the wires in household circuits wrapped in plastic or rubber?

To prevent wire corrosion and electric shock accidents

3. Why is pure water not conductive but ordinary water is?

Ordinary water contains a lot of other substances

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"Conductive Properties of Different Materials" Simple Circuit PPT Courseware 4:

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Update Time: 2024-10-20

This template belongs to Physics courseware Beijing Normal University Ninth Grade Physics Volume 1 industry PPT template

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