"Ohm's Law" PPT courseware 6

Description

"Ohm's Law" PPT courseware 6

review

In the first section on the relationship between current, voltage and resistance we learned:

When the resistance of a conductor is constant, the current in the conductor is proportional to the voltage across the conductor

When the voltage across a conductor is constant, the current in the conductor is inversely proportional to the resistance of the conductor

Summarize

The current in a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.

1. Ohm's law content:

The current in a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.

2. The mathematical expression of Ohm’s law:

3. Use international units in formulas (units must be unified)

Unit of voltage U: V

Unit of resistance R: Ω

Unit of current I: A

4. Deformation formula: U=I R ​​R=U/ I

5. Note: Ohm's law reflects the relationship between I, U, and R in the same circuit at the same time.

2. Apply Ohm’s Law

1. General steps for calculations using formulas:

(1) Read and review the questions (pay attention to the content of known quantities);

(2) Draw a circuit diagram based on the meaning of the question;

(3) Mark the symbols and numerical values ​​of known quantities and the symbols of unknown quantities on the diagram;

(4) Use physical formulas for calculation (the writing format must be complete and standardized).

2. Example question analysis

Example 1 A car lamp has a filament resistance of 30 Ω and is connected to both ends of a 12 V power supply. Find the current flowing through the lamp.

Problem solving steps

(1) Draw a circuit diagram;

(2) List the known conditions and required quantities;

(3) Solve I.

Class summary

Content: The current in a conductor is directly proportional to the voltage across the conductor and inversely proportional to the resistance of the conductor.

Formula: I = U/R

Deformation formula: U=I R ​​R=U/ I

Consolidation exercises

1. Regarding the relationship between current, voltage and resistance, which of the following statements is correct ( )

A. The greater the resistance of a conductor, the smaller the current flowing through the conductor

B． The greater the resistance of a conductor, the greater the current through the conductor

C. The greater the voltage across a conductor, the greater the resistance of the conductor and the greater the current through the conductor

D. When the voltage across the conductor is constant, the smaller the resistance of the conductor, the greater the current flowing through the conductor.

2. According to Ohm’s law formula I=u/r, R=U/ I can be derived. Regarding this formula, the following statement is correct ( )

A. When the voltage across the conductor is zero, the resistance of the conductor is also zero.

B. The greater the voltage across the conductor, the greater the resistance of the conductor.

C. The greater the current in the conductor, the greater the resistance of the conductor.

D. The resistance of a conductor is the property of the conductor itself. Its size has nothing to do with the voltage at both ends of the conductor and the current in the conductor.

3. When a voltage of 4 V is applied to both ends of a nichrome wire, the current flowing through it is 0.2 A, then its resistance is _____Ω. If the voltage at both ends of the alloy wire increases to 16 V, its resistance is _____Ω. If you want to use an ammeter to measure its current, you should use an ammeter with a range of _____A.

4. Regarding Ohm's law, which of the following statements is correct ( )

A. At the same voltage, the current and resistance of a conductor are inversely proportional

B． For the same conductor, the current and voltage in the conductor are proportional

C. Because resistance is a property of the conductor itself, the current is only proportional to the voltage across the conductor

D. The current in a conductor is related to the voltage across the conductor and also to the resistance of the conductor

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Update Time: 2024-07-30

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

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