1. Lesson 6 Lenz’s Law Liceo Alfano

2. Reminder Last time: Currents create magnetic fields, and are affected by magnetic fields Electric motors spin due to the forces from the magnetic field We can make an electromagnet by wrapping a wire around a conductor

3. Magnetic Fields and Current We know that a magnetic field will create a force on a current We know that a current will create a magnetic field Now, we look at one more relationship between currents and magnetic fields Magnets through 3 pipes video Magnet through ring animation

4. What’s Going On? When a conductor feels a changing magnetic field, it induces (creates) a current inside the conductor What does a current create? Lenz’s Law tells us that the current will be created in the direction that opposes the change in the magnetic field – it wants to keep the magnetic field constant

5. Lenz’s Law Example Magnetic field through a ring: as the magnet gets closer, does the field get stronger or weaker? The ring doesn’t want this change – it creates a current to try to keep the field constant, so which way will the current go?

6. Videos Lenz’s law explanation video Lenz’s law animation Ring around a rod video Coil of copper over aluminum plate video Coins falling by magnets video

7. Concept Question The magnetic field shown through the circle of wire is increasing with time. The induced current will be 1) Clockwise 2) Counterclockwise

8. Concept Question The magnetic field shown through the circle of wire is increasing with time. The induced current will be 1) Clockwise 2) Counterclockwise

9. Concept Question The magnetic field shown through the circle of wire is decreasing with time. The induced current will be 1) Clockwise 2) Counterclockwise

10. Concept Question The magnetic field shown through the circle of wire is decreasing with time. The induced current will be 1) Clockwise 2) Counterclockwise

11. Concept Question A square loop falls through a magnetic field as shown. The induced current will be 1) Clockwise 2) Counterclockwise

12. Concept Question A square loop falls through a magnetic field as shown. The induced current will be 1) Clockwise 2) Counterclockwise

13. Concept Question A loop of blue wire is inside a circuit. When the current is turned on, which way will the current in the blue wire go? 1) Clockwise 2) Counterclockwise

14. Concept Question A loop of blue wire is inside a circuit. When the current is turned on, which way will the current in the blue wire go? 1) Clockwise 2) Counterclockwise