1. Direction of Induction
Brought to you by The Right Hand Rule EQ: How is the direction of the induced current and magnetic field determined Pg. 82

2. *Induced Magnetism and current
· A moving magnet induces moving charge
(current) in a wire.
· The induced current in the wire induces a
magnetic field around the wire
· This induced magnetic field experiences a
force from the first magnetic field, repelling or attracting the magnet.

3. Magnetic Flux
The first step to understanding the complex nature of electromagnetic induction is to understand the idea of magnetic flux. B A
Flux is a general term associated with a FIELD that is bound by a certain AREA. So MAGNETIC FLUX is any AREA that has a MAGNETIC FIELD passing through it.

4. Rank the magnitude of magnetic flux that passes through the coil, shown below (edge view) in three different orientations relative to an external magnetic field. Rank from greatest flux to least.
1,2,3 b. 3,2,1 c. (1,3), 2 d.(3,1), 2

5. A current could be induced but only if magnetic field is changing.
Faraday’s Law
A current could be induced but only if magnetic field is changing.
The Father of Electricity, Michael Faraday was born on this day in The English scientist, who is responsible for the discovery of electromagnetic induction, electrolysis and diamagnetism, hailed from a poor family of a blacksmith. Due to weak financial support, Faraday only received basic education.

6. The Right Hand rule
The hand rule is a convenient way to remember directional issues with flow in physics dealing with electricity and magnetism.

7. Symbols
I = Current
B = magnetic field

8. *Right Hand rule Electricity
When a current is moving through a wire a magnetic field is produced
Determine the direction of the magnetic field around a current-carrying wire and vice-versa
-Point your thumb in the direction of the current
-Let your fingers assume a curved position, the magnetic field circling around those wires flows in the direction in which your four fingers point.

9. Choose the correct right hand rule to apply to the correct problem
Closing Task
Choose the correct right hand rule to apply to the correct problem

10. Right Hand rule Electricity Practice

11. *Right hand Rule Electromagnetism
determines the direction of:
the induced current on a moving ring as it enters a magnetic Field
Magnetic field or a current of a solenoid
I- Current
Point your thumb in the direction of the magnetic field (into/out of page or Thumb points north)
let your fingers assume a curved position, the current circling around the ring flows in the direction in which your four fingers point (clockwise or counterclockwise or none if there is not a changing magnetic field).
B- Magnetic field
Points NORTH

12. Right hand Rule Electromagnetism
PrACTICE

13. Lenz’s law
Magnetic flux increases
induced magnetic field opposes entrance
"An induced electromagnetic field generates a current that induces a counter magnetic field that opposes the magnetic field generating the current."
Magnetic flux decreases
induced magnetic field opposes exit

14. Lenz’s Law revisited
"An induced electromagnetic field generates a current that induces a counter magnetic field that opposes the magnetic field generating the current."
In modern terms:
"The induced current is such as to OPPOSE the CHANGE in the magnetic flux within the circuit.“ (keep status quo)
In the figure above, we see that the direction of the current changes. Lenz’s Law helps us determine the DIRECTION of that current.

15. Lenz’s Law & Faraday’s Law
Let’s consider a magnet with it’s north pole moving TOWARDS a conducting loop.
DOES THE FLUX CHANGE?
DOES THE FLUX INCREASE OR DECREASE?
What does this mean?
Yes!
Increase
Binduced
This means that the INDUCED MAGNETIC FIELD around the WIRE caused by the moving magnet OPPOSES the original magnetic field. Since the original B field is downward, the induced field is upward! We then use the curling right hand rule to determine the direction of the current.

16. Right hand Rule Electromagnetism
External magnetic field
Using Lenz Law
Flux
Determine the direction of the external magnetic field.
Determine how the flux is changing. Is it increasing, decreasing, or staying the same?
Determine the direction of an induced magnetic field that will oppose the change in the flux.
Increasing: induced magnetic field points opposite the external magnetic field.
Decreasing: induced magnetic field points in the same direction as the external magnetic field.
Constant: no induced magnetic field.
4. Determine the direction of the induced current. Use the right-hand rule.
Induced magnetic field

17. Right hand Rule Electromagnetism PrACTICE

18. Conceptual Example 9 The Emf Produced by a Moving Copper Ring.
22.5 Lenz’s Law
Conceptual Example 9 The Emf Produced
by a Moving Copper Ring.
There is a constant magnetic field directed
into the page in the shaded region. The field
is zero outside the shaded region. A copper
ring slides through the region.
For each of the five positions, determine whether
an induced current exists and, if so, find its
direction.

19. *Right Hand rule Electromagnetism
When a charge is placed in a magnetic field, that charge experiences a magnetic force That induces a current. The force is perpendicular to both the velocity v of the charge q and the magnetic field B.

20. *Right Hand rule Electromagnetism
When a charge is placed in a magnetic field, that charge experiences a magnetic force That induces a current. The force is perpendicular to both the velocity v of the charge q and the magnetic field B.
Magnetic Field
Charge
Velocity of charge
Force of field

21. Right Hand rule Electromagnetism Practice
Determine the direction of the current (I)
Determine the direction of the magnetic Field (B)
Determine the direction of the force (F) F I

22. In summary
Faraday’s Law found that he could induce a current in a closed wire, but only if the magnetic field through the coil is changing.
Lenz’s Law is part of Faraday’s Law and can help you determine the direction of the current provided you know HOW the flux is changing