"Classification Comprehensive Training" Current and Circuit PPT

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"Classification Comprehensive Training" Current and Circuit PPT

The first part of the content: Combination of textbook knowledge

Breakthrough of core points

1. Frictional electrification, two kinds of charges

1. Frictional electrification: Using friction to charge an object is called ________. The charged object has the property of attracting ________. The essence of frictional electrification is the generation of charge ________.

2. Two kinds of charges: a glass rod rubbed with silk has a ________ charge, and a rubber rod rubbed with fur has a ________ charge. Like charges ________ each other, and dissimilar charges ________ each other. The amount of charge is called ________, and its unit is ________.

3. Electroscope: A device that tests whether an object is charged or not is called _________, which is made based on the principle of __________________.

4. Conductor, insulator: __________ objects that conduct electricity are called conductors, and __________ objects that conduct electricity are called insulators. Metals contain a large amount of ________ and can easily conduct electricity.

2. Circuit Series Circuit and Parallel Circuit

1. Circuit: The _________ of charge forms a current. We define the direction in which the _________ charge moves as the direction of current. Using wires to connect ________, __________, and ________ to form a path through which current can flow is called a circuit. Conditions for continuous current in a circuit: (1) There is ______; (2) The circuit is _____.

The three circuit states are ________ road, ________ road and ________ road.

2. There are two ways of connecting circuits: ________ circuits and ________ circuits. The series circuit has only ________ current paths, and only needs ________ switches to control the circuit, and _______________ between the electrical appliances; the parallel circuit has ________ current paths, and requires ________ switches to control each branch, and between the electrical appliances. ____________.

3. Current Use of ammeter

1. Current: The physical quantity that represents the strength of electric current is ______, represented by the symbol _____. The international unit is ______, referred to as _____, and the symbol is ___. Smaller units include ______ and _______.

2. Use of ammeter: The ammeter should be _________ with the electrical appliance being measured; allow the current to flow in from the ______ terminal and flow out from the ______ terminal; the current to be measured must not ________ the maximum measurement value of the ammeter; it is not allowed to put the ammeter directly Connected to______________.

4. Current laws in series and parallel circuits

The current in a series circuit is ________ everywhere; the current in the trunk of a parallel circuit is equal to the current in each branch.

Comprehensive classification training PPT, the second part of the content: teaching material picture display

Proposition 1: Interaction between charges

(1) As shown in Figure 15-F-1, two glass rods rubbed with silk are brought close to each other and it is found that they ______ each other. This phenomenon illustrates ______________.

(2) When a glass rod rubbed with silk and a rubber rod rubbed with fur are brought close to each other, it is found that they _____ each other. This phenomenon indicates _______________.

(3) A glass rod rubbed with silk and a rubber rod rubbed with fur can be charged. This phenomenon is called ____________, and its essence is that the charge occurs _________.

Proposition 2: Direction of current

As shown in Figure 15-F-2, after closing the switch, the direction of current outside the power supply is from ________ through the electrical appliance to ________.

Proposition point 3: Three states of circuit (path, open circuit, short circuit)

As shown in Figure 15-F-3, when the switch is turned off, the circuit belongs to the ____ circuit; after the switch is closed, the circuit belongs to the ___ circuit; connect the wires to both ends of the right bulb, and after closing the switch, the right The side light bulb does not light up because the right light bulb is ____.

Proposition point 4: Use of ammeter

When using an ammeter, the ammeter must be connected to the electrical appliance under test so that the current flows in from the ________ terminal and flows out from the "-" terminal. The ________ of the ammeter must be chosen correctly. ________Connect the ammeter directly to the poles of the power source! Otherwise, the ammeter will be damaged.

Proposition point 5: Characteristics of parallel circuits

(1) As shown in Figure 15-F-4, close the switch, and the motor and the light bulb in this circuit are _________ connected.

(2) After the motor stops working, the light bulb _________ (optional "not" or "still") can work, indicating that the electrical appliances in the circuit can ____________.

(3) If the current through the power supply is 0.5 A and the current through the motor is 0.4 A, then the current through the light bulb is ________A.

Comprehensive classification training PPT, the third part: reproduction of key experiments

Experiment: Explore the current laws of series and parallel circuits

(1) Experimental circuit diagram: shown in Figure 15-F-6.

(2) Design experiment: To explore the characteristics of current in series and parallel circuits, it is necessary to connect a ______ meter to the electrical appliance under test for measurement. As shown in Figures A and B, measure the currents at A, B, and C respectively for comparison.

(3) Measuring tool: ammeter.

(4) Conduct experiments

① When exploring the current relationship at A, B, and C in the series circuit, connect the ammeter to the three points A, B, and C respectively, measure the currents IA, IB, and IC for comparison.

② When exploring the relationship between the main circuit current and each branch current in a parallel circuit, connect the ammeter to three points A, B, and C respectively, measure the main circuit current IA and branch current IB, IC, and conduct Compare.

(5)Experimental conclusion

①Series circuit: The current everywhere is ______, expressed by the formula as___________.

② Parallel circuit: The main circuit current _________ the sum of the branch currents, expressed by the formula as ____________.

Method 1: Two substances of equal mass are heated for the same time (i.e., they absorb equal amounts of heat). If compared ____________, the substance with a smaller temperature rise has a stronger ability to absorb heat;

Method 2: Two substances of equal mass raise the same temperature and compare ____________ (i.e., the amount of heat absorbed). The substance that absorbs more heat has a stronger ability to absorb heat.

⑤ If you want to reduce the heating time by raising the same temperature, the approach you can take is ____________________.

(6)Evaluation communication

① In the experiment, light bulbs of different specifications should be replaced to measure several sets of data for the purpose of ____________________________.

② During the experiment, Xiao Zhang found that the light bulb L1 in Figure A was brighter than L2, so Xiao Zhang thought that "every time the current flows through an electrical appliance in the series circuit, the current will be weaker." Please do not add any equipment and find a way to prove that Xiao Zhang’s point of view is wrong.

Proof method: __________________________________________________________________________________.

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Update Time: 2024-10-06

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