"Current" Simple Circuit PPT Courseware 4

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"Current" Simple Circuit PPT Courseware 4

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current

The formation of current In a circuit, due to the action of the power supply, free charges can move in a directional manner. This directional movement of free charges forms a current.

The direction of current is defined as the direction of _______ directional movement as the direction of current

Unit of current The symbol of current is represented by the letter _______. The unit of current is _______, abbreviated as ampere, symbol A. 1 A=_______ mA,1 A=_______μA

Ammeter

Function: measure the size of _______ in the circuit

Symbol _______

Measuring range Commonly used ammeters have _______ binding posts and two measuring ranges, namely _______,

Rules of use (1) The ammeter must be _______ in the part of the circuit being measured; (2) The "+" and "-" terminals of the ammeter must be connected correctly, and the current must flow from the "_______" terminal to the "_______" terminals flow out; (3) The measured current should not exceed the _______ of the ammeter. When the measured current cannot be estimated in advance, the _______ method can be used to determine whether the measured current exceeds the range; (4) Absolutely not allowed Directly connect the ammeter _______ to the two poles of the power supply without using electrical appliances; (5) When reading, the line of sight should be with the dial.

Features

Series Circuit Current in a series circuit_______

Parallel Circuit The current in the trunk of a parallel circuit is equal to _______

[Example] A student hopes to study the current pattern of a series circuit by comparing the readings of ammeters at different locations in the circuit. The connected circuit diagram is shown in Figure A. After closing the switch, the deflection of the two ammeter pointers is shown in Figure B.

(1)The reading of ammeter A2 is _____.

(2) The student found that the deflection of the pointer of ammeter A1 was smaller than that of ammeter A2, so he thought that "every time the current in the series circuit flows through an electrical appliance, the current will weaken a little." Please point out the reasons for his misjudgment.

(3) After connecting the circuit, both light bulbs are on. Due to the messy wiring, it is not possible to determine whether the circuit is connected in series or in parallel. Are the following two simple judgment methods feasible? Please fill in the blanks in the table as "feasible" or "not feasible" ".

Method Operation Phenomenon Conclusion Is the method feasible?

Method 1: Take out one of the light bulbs from the lamp holder and the other light goes out. The two lights must be connected in series.

Method 2: Disconnect any one wire and the two lights will go out. The two lights must be connected in series.

Analysis: (1) From the current indication, it can be read that the indication of ammeter A2 is 0.4 A; (2) The different deflection degrees of the two ammeters are due to the different ranges used by the two ammeters. They cannot be obtained based on only one measurement data. It is concluded that the equipment selection for the simultaneous experiment is not appropriate. The same ammeter should be selected to measure the current at different locations. After multiple measurements, judgment and induction are made; (3) According to the characteristics of series circuits and parallel circuits, method 1 is It is feasible, but in method 2, if the wire in the main circuit is disconnected in the parallel circuit, both lights in parallel will go out, so it is not feasible to use this method to judge whether the two lights are connected in series or in parallel.

Answer: (1) 0.4 A (2) Ammeters A1 and A2 have different ranges. (3) Feasible or not feasible

1. Among the four scientists shown in the picture, the one who named the unit of electric current is ()

2. What is the correct relationship between the units of current, amperes, milliamps, and microamps ()

A.1 A=102 mA　B.1 A=106 μA

C.1 mA=102 μA D.1 μA=10-3 A

3. When a classmate used an ammeter to measure the current of a circuit, he used two terminals as shown in the picture. The following statement is correct ()

A. The measuring range of the ammeter is 0.6~3 A

B. The measuring range of the ammeter is 0~0.6 A

C. The measuring range of the ammeter is 0~3 A

D. It cannot be used to measure current, and it cannot talk about the range.

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Update Time: 2024-11-22

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

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