"How to Understand and Measure Voltage" explores simple circuit PPT courseware

Description

"How to Understand and Measure Voltage" explores simple circuit PPT courseware

learning target

1. Know what voltage is, know that a power supply is a device that provides voltage, and know the units of voltage: volts, kilovolts, and millivolts.

2. Know common power supplies and some voltage values.

3. A voltmeter will be used to measure voltage.

Core test point: connection and reading of voltmeter.

Preview before class

1. (2015•Pudong New Area Model) Voltage is the reason why free charges move directionally to form ________. The voltage of an ordinary new dry cell battery is ___ volts. Physics stipulates that current flows from the ___ pole of the power supply.

2. Pay attention to the following when using the voltmeter correctly:

(1) Current can only flow in from the ___ terminal of the voltmeter;

(2) The voltmeter should be ___ connected in the circuit;

(3) The measured voltage ______ exceeds the range of the voltmeter;

(4) When reading, you should clearly recognize the measurement range used and its corresponding graduation value. If you choose the range of 0 to 15V, the graduation value is ___;

(5) If the voltmeter is directly connected to the two poles of the power supply, what is measured is the voltage at both ends of ______.

Lectures in class

Knowledge point 1. Power supply and voltage

(1) Power supply: A power supply is a device that provides voltage to both ends of electrical appliances. It can also be said that a power supply is a device that provides electrical energy; common power supplies include dry batteries, batteries, generators, etc.

(2) Voltage: Voltage is the cause of current in a circuit.

①Unit of voltage: The international unit of voltage is volt (V, referred to as volt). Commonly used units include millivolt (mV), microvolt (μV), kilovolt (kV), etc. 1 kV=1 000 V, 1 V=1 000 mV

② Several common voltage values: the voltage of a dry battery (No. 5, No. 7) is 1.5 V; the voltage of each battery is 2 V; the voltage of our household circuits is 220 V; the safety voltage for the human body is not high At 36 V. Note: Voltage is the cause of current, but it does not necessarily mean that there is current if there is voltage. It also depends on whether the circuit is a path; the voltage cannot be said to be the voltage at which point. When expressing the voltage, it must be specified "where". "The voltage across an electrical appliance" or "the voltage between two points".

[Typical Example 1] Regarding voltage, which of the following statements is correct ( )

A. Only closed circuits have voltage, open circuits have no voltage

B． Current creates a voltage in a circuit

C. As long as there is voltage across the circuit, there will be current in the circuit

D. For there to be current in a circuit, there must be voltage across the circuit

[Typical Example 2] The most realistic of the following data is ( )

A. The voltage of a new dry cell battery is 1.5V

B． The temperature in the classroom in winter is about 60℃

C. The propagation speed of light in vacuum is 340m/s

D. The safe voltage for the human body is not higher than 220 V

Knowledge point 2. Voltmeter and its use

A voltmeter is an instrument that measures voltage. Its symbol in the circuit is. A common voltmeter has three binding posts and two ranges (0~3 V, O~15 V). The dial of the meter is marked with the letter "V" ,As shown below.

(1) Range of voltmeter

The voltmeter in the laboratory has 3 binding posts and 2 ranges. The terminals marked with "-" are shared. When connecting the circuit, the current flows in from the "+" terminal and the current flows out from the "-" terminal.

①As shown in the figure above for the voltmeter, the two ranges share a "-" terminal, and the two terminals marked "3" and "15" are both positive terminals. When two binding posts "-" and "3" are used, the measuring range is "O~3 V", and each small grid represents 0.1A; when two binding posts "-" and "15" are used, the measuring range is "0~15 V", each small grid represents 0.5V.

②When the two different measurement ranges of "0~3 V" and "0~15 V" are selected, if the pointer deflection position is the same, the indication will be 5 times related.

(2) Rules for using voltmeter

① Before measuring, check whether the pointer is aligned with the zero mark. If there is a deviation, zero calibration is required first.

② When measuring voltage, the voltmeter must be connected in parallel at both ends of the circuit being measured, and the current must flow in from the "+" terminal of the voltmeter and flow out from the "-" terminal, otherwise the pointer will deflect in the opposite direction or even bend. pointer.

In-class testing

1. Which of the following statements is wrong ( )

A. A power supply is a device that provides voltage

B． Voltage is what causes current to form

C. As long as there is voltage at both ends of the circuit, there must be current

D. Electric current is caused by the directional movement of charges

2. As shown in the figure is the dial of a double-range voltmeter. When a smaller range is used, the indication of the pointer position in the figure is _______V; when a larger range is used, the indication of the pointer position in the figure is _______V;

3. (2014•Yiyang) As shown in the picture is the circuit used by Xiao Ming to measure the voltage at both ends of the small light bulb L1. There is a wire connected wrongly in the picture. The wrong wire is ( )

A. Wire 1

B． Wire 2

C. Wire 3

D. Wire 4

4. When Xiaoning was exploring and practicing using a voltmeter, she connected the voltmeter into the circuit as shown in the picture. What happens when the switch is closed is ( )

A. The light bulb is on and the voltmeter is reading

B． The light bulb is on and the voltmeter has no reading

C. The light bulb does not light up, but the voltmeter shows a reading

D. The light bulb does not light up and the voltmeter has no indication.

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

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

"How to Recognize and Measure Voltage" Exploring Simple Circuit PPT Courseware 2 Voltage is the cause of the formation of current. Why does the small light bulb light up when the switch is closed (click the switch)? How is electric current formed? 1. Water flow: water height difference (water level difference, water pressure difference) water pressure...

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Update Time: 2024-09-09

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

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