Lesson plan

Topicmc83df464fe5a53e9_1528449000663_0Topic

Electrical receivers connected in series

Levelmc83df464fe5a53e9_1528449084556_0Level

Second

Core curriculummc83df464fe5a53e9_1528449076687_0Core curriculum

VI. Electricity. The student:

13) draws diagrams of electric circuits consisting of one energy source, one electrical receiver, meters and switches; uses graphical symbols of these elements.

Timingmc83df464fe5a53e9_1528449068082_0Timing

45 minutes

General learning objectivesmc83df464fe5a53e9_1528449523725_0General learning objectives

Derivation of the formula for equivalent resistance in a series connection.

Key competencesmc83df464fe5a53e9_1528449552113_0Key competences

1. Defining equivalent resistanceequivalent resistanceequivalent resistance.

2. Experimental test of voltages on resistors connected in series.

3. Experimental verification of the formula for equivalent resistance in a series connectionseries connectionseries connection.

Operational (detailed) goalsmc83df464fe5a53e9_1528450430307_0Operational (detailed) goals

The student:

- defines the concept of equivalent resistance,

- knows and applies the formula for equivalent resistance in a series connection.

Methodsmc83df464fe5a53e9_1528449534267_0Methods

1. Discussion developing in the course of common problem solving by a class or group.

2. Organizing and applying the results obtained in new tasks of a practical or theoretical nature.

Forms of workmc83df464fe5a53e9_1528449514617_0Forms of work

1. Work in groups during the experiment.

2. Work in groups on the formulation and verification of the research hypothesis.

Lesson stages

Introductionmc83df464fe5a53e9_1528450127855_0Introduction

Prepare answers to introductory questions for the lesson.

1. What is electric current?

2. Introduce Ohm's law.

3. Define the resistance of the conductor.

4. What will happen to the resistance of the conductor when we increase the voltage applied to it?

Proceduremc83df464fe5a53e9_1528446435040_0Procedure

When resistors are connected in series?

[Illustration 1]

The serial connection forces the same current. There is no possibility that a current of different intensity flows through two selected resistors. This would be contrary to the principle of energy conservation.mc83df464fe5a53e9_1527752263647_0The serial connection forces the same current. There is no possibility that a current of different intensity flows through two selected resistors. This would be contrary to the principle of energy conservation.

[Slideshow]

Experiment 1

Research hypothesis:

In a series connectionseries connectionseries connection of resistors, the sum of voltages on individual resistors is equal to the voltage supplying the circuit.

1. You will need several different resistors, an ammeter, a voltmeter and a voltage source to perform the experiment.

2. Build the system according to the diagram below.

[Illustration 2]

3. Perform voltage measurements on individual resistors and supply voltage

4. Measurements results should be entered into the measurement table.

[Table 1]

5. In order to eliminate errors during the experiment, perform several measurements, preferably each time rearranging the order of the resistors.

6. After completing the experiment, draw the appropriate conclusions.

Conclusion:

In a series connectionseries connectionseries connection of resistors, the sum of voltages on individual resistors is equal to the supply voltage:

U_{1} + U_{2} + U_{3} + U_{4} + U_{5} = U_{supply}

Definition of equivalent resistanceequivalent resistanceequivalent resistance.

The equivalent resistance of the resistors circuit is equal to the resistance of such a resistor which used instead of the resistor circuit will not change the current flowing from the voltage source.

Derivation of the formula for equivalent resistance in a series connection.

Consider a circuit of resistors connected in series.

[Illustration 3]

Let the voltages on the resistors equal respectively: $U_{1}, U_{2}, U_{3}, U_{4}, U_{5}$ . The current flows in the system with the intensity I. Under Ohm's law we have:

U_{1} = I \cdot R_{1}

U_{2} = I \cdot R_{2}

U_{3} = I \cdot R_{3}

U_{4} = I \cdot R_{4}

U_{5} = I \cdot R_{5}

If we use substitute equivalent resistanceequivalent resistanceequivalent resistance instead of all resistors, then:

U_{supply} = I \cdot R_{equiv}

Substituting above relations into the formula:

U_{1} + U_{2} + U_{3} + U_{4} + U_{5} = U_{supply}

after simplification it leads to the final result:

R_{1} + R_{2} + R_{3} + R_{4} + R_{5} = R_{equiv}

Final conclusion:

In a series connection of resistors, equivalent resistance is the sum of resistances of individual resistors.mc83df464fe5a53e9_1527752256679_0In a series connection of resistors, equivalent resistance is the sum of resistances of individual resistors.

Experiment 2

Research hypothesis:

In a series connection of resistors, equivalent resistanceequivalent resistanceequivalent resistance is the sum of resistances of individual resistors.

1. You will need several different resistors, an ammeter, a voltmeter and a voltage source to perform the experiment.

2. Build the system according to the diagram below.

[Illustration 4]

3. In the way known to you, determine the resistances of individual resistors.

4. Calculate the total resistance of the resistor system.

5. Enter the results into the measurement table.

[Table 2]

6. In order to eliminate errors during the experiment, perform several measurements, preferably each time rearranging the order of the resistors.

7. After completing the experiment, draw the appropriate conclusions.

Conclusion:

If the experiment was performed correctly, then within the limits of measurement errors:

R_{1} + R_{2} + R_{3} + R_{4} + R_{5} = R_{total} = R_{equiv}

It is, therefore, a confirmation of the formula derived theoretically.

Lesson summarymc83df464fe5a53e9_1528450119332_0Lesson summary

- In the series connectionseries connectionseries connection, a current I flows through the closed electrical circuit. It is the same in any point of the serial circuit.

- The voltage between the ends of the resistors connected in series is equal to the sum of the voltages between the ends of each of them.

- The total resistance (equivalent resistanceequivalent resistanceequivalent resistance) in the series connection is the sum of the resistances of individual resistors:

R = R_{1} + R_{2} + R_{3} + . . .

Selected words and expressions used in the lesson plan

equivalent resistanceequivalent resistanceequivalent resistance

principle of charge conservationprinciple of charge conservationprinciple of charge conservation

series connectionseries connectionseries connection

voltage dividervoltage dividervoltage divider

voltage dropvoltage dropvoltage drop

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equivalent resistance1

series connection1

principle of charge conservation1

voltage divider1

voltage drop1

Scenariusz

Topicmc83df464fe5a53e9_1528449000663_0Topic

Lesson stages

Selected words and expressions used in the lesson plan