1. Learning Objectives
I can describe electric current and how voltage is applied to that current.
I can compare direct current to alternating current and describe some devices that use each current.
I can describe factors that create resistance and its relationship with electric current.

2. Ohio New Learning Standards for Science
Ohio 7th Grade, Physical Science #3 (7.SIA.3) – Energy can be transferred through a variety of ways.

3. Lesson Opener

4. Unit 8, Lesson 5 – Electric Current
What is an electric current?
- using a smartphone, iPad, iPod, laptop, flat screen, or e-reader depends upon moving electrical charges, called electrical energy, to power them
- electrical charges flow through wires in those devices & that rate of electrical charge flow is called electric current

5. Unit 8, Lesson 5 – Electric Current
How is electric current measured?
- electric current is the amount of electron charge that passes a location in a wire every second

6. Unit 8, Lesson 5 – Electric Current
- electric current is measured in units called amperes, or amps (A)
- a wire with a current of 2A has twice as much charge passing by each second as a wire with a current of 1A

7. Unit 8, Lesson 5 – Electric Current
What are two kinds of current?
- two kinds of electric current are direct current (DC) and alternating current (AC); both carry electrical charges, but they differ in how the charges move

8. Unit 8, Lesson 5 – Electric Current
Complete #7, pg.591

9. Unit 8, Lesson 5 – Electric Current
What affects electric current?
- two factors that can affect the current in a wire are voltage and resistance
- voltage is the amount of work required to move each unit of charge between two points
- higher voltage produces a higher rate of flow of electric charges in a given wire

10. Unit 8, Lesson 5 – Electric Current
- voltage is expressed in units of volts (V)
- voltage is sometimes called “electric potential” because it’s a measure of the electrical potential energy per unit charge!
Complete #7, pg.592

11. Unit 8, Lesson 5 – Electric Current

12. Unit 8, Lesson 5 – Electric Current
- some materials do not allow electric charges to move freely
- the opposition to the flow of electric charge is called resistance and is expressed in ohms (), the Greek letter for omega
- higher resistance at the same voltage results in lower current!

13. Unit 8, Lesson 5 – Electric Current
What affects electrical resistance?
- a material’s composition affects its resistance (silver & copper have low resistance, whereas iron & nickel have high resistance)
- electrical insulators such as plastic have such high resistance that electric charges cannot flow in them at all (this is why most wires are coated in plastic!)

14. Unit 8, Lesson 5 – Electric Current
- other factors that affect the resistance of a wire are thickness, length, and temperature
- a thin wire has higher resistance than a thicker wire
- a long wire has higher resistance than a shorter wire
- a hot wire has higher resistance than a cooler wire
Complete #10, pg.593

15. Unit 8, Lesson 5 – Electric Current

16. Visual Summary

17. Exit Question
What happens to the electric current in a wire as voltage is increased?