1. The motor effect - - - - + + + +
When a current carrying wire is placed in a magnetic field,
it will experience a force.
This is called the motor effect. S + - + - + - N + -

2. Magnetic Force on a Current-Carrying Conductor
Graphics from Ted Vittitoe

3. Right hand ‘Slap’ rule
fingers ~ field
Thumb ~ current
Slap – force direction

4. The left-hand motor rule
Note:
Magnetic field direction is from NORTH to SOUTH
Current direction is from PLUS to MINUS

5. Force on an Electric Current in a Magnetic Field
A current-carrying wire in a B-field wire experience a Force

7. N S A + -
Which diagram below describes the situation at point A? (All are at right angles)
Construct a diagram that describes the situation at point A showing current, B field and the force of the magnetic field on current. 3
current
B field A 1
current
B field A 2
current
B field A

8. A Force occurs due to the combination of magnetic fields

9.  + =
neutral point
Make sure you don’t confuse these two separate effects:
1) A Current produces its own Magnetic Field
2) A Magnetic Field exerts a force on a Current carrying wire – Why?!

10. Confirm with RHR...

11. Confirm with RHR...

12. Insert the missing information
Q1. Force direction ?
Q2 Current direction ? N S S N
Q3 N and S poles ?
Q4 Force directions ? N S N S
Note:
means current out of the page
means current into the page

13. A 1. 5-m length of wire carrying 4
A 1.5-m length of wire carrying 4.5 A of current is oriented horizontally. At that point on the Earth’s surface, the dip angle of the Earth’s magnetic field makes an angle of 38° to the wire. Estimate the magnitude of the magnetic force on the wire due to the Earth’s magnetic field of at this point. q Be I

14. Suppose a straight 1.00-mm-diameter copper wire could just “float” horizontally in air because of the force due to the Earth’s magnetic field which is horizontal, perpendicular to the wire, and of magnitude What current would the wire carry? mg
ILB Be I

15. Find the magnitude and direction of the current that must flow through the red bar in order to remove the tension from the springs. x
B = .440 T L
L = 62.0 cm
m = 13.0 g