## Ohm's Law

### Lesson Plan

#### State Standards:

5.2 Interpret and apply Coulomb's law.

5.3 Explain the difference in concept between electric forces and electric fields.

5.5 Identify appropriate units of measurement for current, voltage, and resistance, and explain how they are measured.

#### Essential Question:

How do current, voltage, and resistance relate to one another?

#### Lesson Question:

How do current, voltage, and resistance relate to one another?

#### Introduction:

How do you light a light bulb? What is electricity? What is it that moves and gives the bulb energy? What is current, voltage, and resistance? If you add more batteries to a circuit what happens to a light bulb? If you add more light bulbs what happens? Why?

#### Task:

You job is to figure out how a circuit works - from the very basic to more complex relationships. First you will just try to light a bulb. Then you create and implement an investigation to uncover more properties of a circuit.

#### Lesson Experiences:

- Start with just one battery, one bulb and one wire. Try to see if you find two ways to get the bulb to light. Once you have successfully lit the bulb, draw detailed diagrams for each set-up. Then draw two diagrams for set-ups that did not light the bulb.
- Once you have successfully lit the bulb watch this video for some background information on circuits:

**3.**Use the PHET simulation to explore current voltage and resistance and the relationships between them.

- Start by constructing a simple circuit with just one bulb, one battery and a few wires.
- Then add another bulb and notice how the brightness of the bulbs change and the flow of electrons change. Record your observations in your notebook.
- Experiment by changing the number of light bulbs and batteries a few times. Note how the brightness of the bulbs and the flow of the electrons change each time.
- Write down two or three sentences that generalize how the number of light bulbs affect the flow of electrons and the number of batteries affect the flow.
- If the resistance of the circuit is represented by the number of light bulbs, what represents the current and voltage?

4. Take a short quiz online.

- You need to provide your name and e-mail address so that I can see your results.
- Answer the five questions as best as you can on your own.

- Your first step is to write a procedure. How do voltage and current relate? Work with your partner to design an investigation that will help you understand their relationship. Think about how you can vary the voltage in a circuit. How will you observe the effect of that on the current in the circuit? What will you do to keep track of the information you are getting? How will you record and organize it? How will you display the relationship? When you have come up with a procedure show it to your teacher for approval before you begin your investigation.
- Carry out your investigation. Keep track of your data in an organized manner (a table or chart). Then display it in a meaningful way (graph).
- Look at your graph. Is the relationship between current and voltage linear? direct or indirect? How do we model that sort of relationship with an equation?
- How will you modify your investigation to explore how voltage and resistance relate? Repeat the investigation again but this time look at the relationship between voltage and resistance. Again model that relationship with an equation.
- How can you combine your equations to get Ohm's Law? Ohm's Law is V = IR. How do your results compare with that? Do they agree? Why/why not?

#### Conclusion:

Ohm's Law is V = IR. In your own words, what does Ohm's law mean? What does it look like in a circuit? What can you change in a circuit and how will it affect the other parts?

#### Assessments:

-Students will receive 5 points for lighting the bulb (1 for lighting it and 1 for each diagram drawn)

-5 points for the zoho quiz

-20 points for the lab report

#### Resources:

**PHET-simulation****ZoHo****YouTube****Wires,****bulbs,****batteries and resistors****Wikispaces****Handouts on investigations****Lab rubric**

**Image Credit**: Ohm's Triangle