Explore the concept of electrical resistance by creating series and parallel circuits with a variety of resistors.
Students demonstrate how the resistance of a circuit varies when resistors are placed in series versus parallel. They complete calculations based on their group’s data.
Each group will need:
Any electrical component with electrical resistance restricts the flow of electrons in a circuit and transforms electrical energy into other forms of energy.
A resistor is an electrical component with a specific resistance value. Resistors can be used to control current or to provide a specific voltage and current to other components in a circuit.
Students should use different strengths of resistors in their circuits. If the resistors have the same resistance value in a series circuit, the voltage drop in each resistor will be the same (each will be half of the applied voltage). For parallel circuits, the current will be the same through each resistor, although each will be half of the total current. Using resistors with different values emphasizes how the voltage and current change in series and parallel circuits.
Students should be able to recognize the following relationships emerging from the data collected during their investigations:
Table A - Series Circuit Measurements
*Resistor values will depend on resistors used.
**Sum of the voltages across the three resistors should equal approximately 3.0 V.
Table B - Parallel Circuit Measurements
* Resistor values will depend on resistors used.
1. Calculate the total resistance of your series circuit using Ohm’s Law (R = V / I). Be sure to use the voltage across the dry cells. Show your calculations.
2. How does the resistance calculated above compare to that of the individual resistors used in the circuit?
3. How does the voltage compare across each resistor in a series circuit?
4. Add the voltages from across each of the resistors. How does this total compare to the voltage of the dry cells?
5. Using Ohm’s Law, calculate the total resistance of your parallel circuit. Be sure to use the voltage across the dry cells as V in your calculation.
6. How does the resistance calculated above compare to that of the individual resistors used in the parallel circuit?
7. How does the voltage compare across each resistor in a parallel circuit?
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