"How to Understand and Measure Current" Exploring Simple Circuit PPT Courseware 2

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"How to Understand and Measure Current" Exploring Simple Circuit PPT Courseware 2

what is current

Pedestrians on the road move in a certain direction to form a "flow of people"

Vehicles on the road move in a certain direction to form "traffic flow"

The flow of water through the turbine causes the turbine to rotate. The water in the water pipe moves in a certain direction to form a "flow". Similarly, the light bulb will glow because there is _____ current flowing through the circuit.

How is electric current formed?

what is current

1. The formation of electric current: it is the directional movement of electric charges in a conductor.

2. Current direction: Specifies the direction in which positive charges move directionally.

3. Current flow path: positive pole of power supply → electrical appliance → negative pole of power supply.

Activity 1: Compare the strength (size) of the current

Phenomenon: The brightness of the same light bulb is different when it is powered on, indicating that the current is strong or weak.

The brighter the bulb, the greater the current.

Current intensity (current): Indicates the size of the current

Represented by the letter I

Units of current: Amperes, milliamperes, microamps

Unit conversion relationship:

1 A = 1000 mA 1 mA = 1000 microA

Unit conversion

1.2 A=_________mA=_________μ A

0.06 A=_________μ A

500mA=___________A

1.5x103 μ A=_________A=_________mA

practise:

1.0.5 Ampere=_______mA=_______microampere

2. 200 mA = _______ amps = _______ microamps

3. 10,000 microamps =_______amperes

4. "0.15A" is most likely the current of which of the following household appliances is working: ( )

A. Household refrigerator. B. Household air conditioners.

C. Ordinary lighting. D. Ordinary calculator.

The "ten" and "one" terminals must be connected correctly

The current must flow from the "ten" terminal into the ammeter

The ammeter flows from the "one" terminal

The measured current cannot exceed the maximum measured value

When the measured current exceeds the maximum measurement value of the ammeter, not only will the current value not be measured, but the pointer of the ammeter will be bent, or even the ammeter will be burned out.

If the magnitude of the measured current cannot be estimated in advance, first quickly touch the terminal of the ammeter with a wire end of the circuit to see if the deflection of the pointer is within the range. If it exceeds the range, it is necessary to use an ammeter with a larger range.

Do not short-circuit the ammeter

It is absolutely not allowed to connect the ammeter directly to the two poles of the power supply without using electrical appliances. Otherwise, the ammeter will burn out quickly.

Instructions for use of ammeter

The internal structure of the ammeter is relatively precise, and improper use can easily damage the ammeter.

1. Check whether the pointer points to zero before use.

2. The ammeter must be connected in series in the circuit.

3. Make the current flow in from the “+” terminal of the ammeter and flow out from the “-” terminal.

4. It is absolutely not allowed to connect the ammeter directly to the two poles of the power supply.

5. The measured current cannot exceed the range of the ammeter.

Class exercises

1. The circuit shown in Figure 1 uses an ammeter to measure the current in the lamp L. The correct connection is ( )

2. When connecting the ammeter to the circuit, sometimes it is necessary to test the touch. The purpose is ( )

A. Check whether the ammeter is intact.

B. Check whether the ammeter is connected correctly.

C. Check whether the entire circuit is connected correctly.

D. Select the range that is most suitable for the current being measured.

Practice to achieve standards

1. If you want to know the current flowing through a certain circuit, you can use an ammeter to measure it. As shown in the figure, an ammeter is used to measure the current through L1. Which of the following circuit diagrams is correct ( )

2. When using an ammeter, if the positive and negative terminals are connected reversely, the consequences will be: ( )

A. The electrical appliance was burned out B. The power supply was burned out

C. The pointer is reversed. D. Normal reading is possible.

3. A classmate used the "0-0.6A" range to measure the current of a certain circuit. Because the scale on the lower row was blurry, he read the data on the upper row as 2.4A, so the actual current of the circuit is _____A.

summary:

1. Current (I)

2. Current unit: Ampere A

In memory of French Ampere

3. Unit conversion: 1A=1000mA 1mA=1000μA

4. Ammeter:

Large range 0—3A 0.1A 1A/10=0.1A

Small range 0—0.6A 0.02A 0.2A/10=0.02A

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For more information about the PPT courseware "Exploring How to Recognize and Measure Current in Simple Circuits", please click the Explore How to Recognize and Measure Current in Simple Circuits ppt tag.

"How to Understand and Measure Current" explores simple circuit PPT courseware:

"How to Understand and Measure Current" Exploring Simple Circuit PPT Courseware Learning Objectives 1. Know the direction of current and the units of current. 2. Understand ammeters and be able to use them correctly to measure current. 3. Understand common current values ​​in life. Core test point: Ammeter..

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Update Time: 2024-09-26

This template belongs to Physics courseware Guangdong and Shanghai Edition Ninth Grade Physics Volume 1 industry PPT template

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