"Measurement of Current" Current and Circuit PPT Courseware 2

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"Measurement of Current" Current and Circuit PPT Courseware 2

1. Current

Meaning: Indicates the strength of the current, or the size of the current, represented by the capital letter I.

Unit: Ampere, abbreviated as A, symbol A.

Conversion: 1A=103mA 1A=106μA

Common currents: P45 "little information"

Human body's reaction to electric current

0.6mA~1.5mA Finger starts to feel numb and no feeling

2mA~3mA Fingers feel strong numbness and no feeling

5mA~7mA Finger muscles feel spasm, fingers feel burning and tingling

8mA~10mA Finger joints and palms feel pain. It is difficult to disconnect the hand from the power supply, but the hand can still be disconnected from the power supply. Burning sensation increases

20mA~25mA Fingers feel severe pain, rapid paralysis, unable to get rid of the power source, difficulty breathing. The burning increases and the muscles of the hand begin to spasm.

50mA~80mA Respiratory paralysis, atrium begins to tremble, strong burning pain, hand muscle spasm, difficulty breathing

90mA~100mA Respiratory paralysis, lasting for 3 seconds or longer, cardiac paralysis or atrium stops beating Respiratory paralysis

2. Ammeter

Function: Measure the size (strength) of current.

The ammeter has almost no obstruction to the current, similar to a wire, so it cannot be directly connected to the positive and negative poles of the power supply, or connected in parallel to both ends of the electrical appliance.

3. Use of ammeter

1. Observe: zero scale line, range, and graduation value.

2. Zero adjustment: Make the pointer point at the zero scale line, otherwise the reading will be inaccurate.

3. Connection: Connect the ammeter in series to the circuit under test so that the current flows in from the positive pole and flows out from the negative pole, otherwise the pointer will reverse.

4. Selection: When the current cannot be estimated, a large-range binding post should be connected to the circuit first to avoid burning out the ammeter.

5. Test touch: quickly close and open the switch, and observe the deflection angle of the ammeter pointer.

6. Reading: Wait until the pointer is stable before reading. When reading, the line of sight and the scale surface are perpendicular to the corresponding scale value line.

7. Counting: First determine the measuring range and graduation value, then read the large scale value, then multiply the small division value by the division value, and finally add them up.

Common faults of ammeters:

1. The ammeter pointer deviates to the left: the positive and negative terminals of the ammeter are connected reversely.

2. The ammeter pointer is shifted to the right end: the ammeter range is selected too small.

3. The ammeter pointer deviates very slightly to the right: the ammeter range is selected to be large, and a small range should be used for accurate measurement.

4. The ammeter readings differ by 5 times: the current in the small range is mistakenly read into the large range.

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For more information about the "Measurement of Current, Current and Circuits" PPT courseware, please click on the "Measurement of Current ppt Current and Circuits ppt" tag.

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"Measurement of Electric Current" PPT Part One Content: Teaching Objectives 1. Understand the basic concepts of electric current. 2. Know the current values ​​of some household appliances. 3. Practice and master the current measurement methods and procedures. 4. Able to read ammeter according to standard methods. 5. Can press the button...

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Update Time: 2024-06-29

This template belongs to Physics courseware People's Education Edition Ninth Grade Physics Complete Book industry PPT template

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