University of Arkansas - AgriScience Project

AGRISCIENCE EXERCISE

PHYSICAL SCIENCES IN AGRICULTURE

Key Concept: Electricity and Electronic Systems

Sub-Concept: Electric Circuits

Agricultural Application: Basic electronic principles are applied in common agricultural equipment.

Exercise: Determining Total Resistance in Series and Parallel Circuits

Applied Principle(s): Basic principles of electricity

Goals:

  1. Describe the relationship between the resistance of individual loads and the total resistance in series, parallel, and series-parallel circuits.


Materials:



References: Refer to any basic electricity or high school physics textbook for further information

Procedures for Conducting the Activity:

1. Divide the class into pairs of students, and provide each with a data sheet and the necessary materials for this exercise.

2. Instruct the students to complete the activity as directed on their data sheets. You may wish to monitor their progress as they work; however, it is suggested that the students be left to follow the instructions and complete the activity on their own.

3. Once all groups have completed the exercise, discuss the answers to the discussion questions as a class. Be sure to make note of the practical agricultural applications of the principles demonstrated.



AGRISCIENCE EXERCISE

- Determining Total Resistance in Series and Parallel Electrical Circuits -

Student Data/Instruction Sheet

1. Gather the following materials:

2. Use the resistance function of the DMM to determine the resistance of each resistor. Write these resistance values on pieces of masking tape and attach the tape to the appropriate resistor.

3. Connect the resistors in series as shown below:











4. Record your estimate of the total resistance of this series circuit below:

Expected Total Resistance (Series Circuit) = __________ Ohms

5. Determine the actual total resistance of your series circuit by connecting the DMM (set for resistance) in the circuit as shown:











Actual Total Resistance (Series Circuit) = __________Ohms



6. Connect the resistors in parallel as shown below:



















7. Record your estimate of the expected total resistance of this parallel circuit:

Expected Total Resistance (Parallel Circuit) = _______________Ohms

8. Determine the actual total resistance of this parallel circuit by connecting the DMM (set for resistance) in the circuit as shown below:





























Actual Total Resistance (Parallel Circuit) = _______________ Ohms



9. Connect the resistors to form a series-parallel circuit as shown below:



















10. Record your estimate of the expected total resistance of this parallel circuit .

Expected Total Resistance (Series-Parallel Circuit) = _______________ Ohms

11. Determine the actual total resistance of this series-parallel electrical circuit (set for resistance in the circuit as shown below:





























Actual Total Resistance (Series-Parallel Circuit) + __________ Ohms

12. Disassemble the circuit and return your supplies and equipment to their proper locations.









13. Answer the following discussion questions:

a. Describe the difference in the total resistance of series and parallel electrical circuits:













b. Develop an equation that can be used to predict the total resistance of a series circuit.











c. Develop an equation that can be used to predict the total resistance of a parallel circuit.















d. How are house lights wired (series or parallel)? Why is this?















e. Describe how to estimate the total resistance of a series-parallel circuit.























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