1. Starter… + +
If I move one charges object close to the other, what happens?
…and Why?
Hint: Think about the field lines around the charges

2. Starter… If I move one magnet close to the other, what happens?
S N
N S
If I move one magnet close to the other, what happens?
…and Why?
Hint: Think about the field lines around the magnet

3. Magnetic Fields Magnetic Field goes from N to S outside the magnet
Magnetic Field Strength, or Magnetic Flux Density, B is measured in Tesla, T

4. Magnetic Flux Density in Solenoid
Magnetic Flux Density, B, in a solenoid is
Uniform inside the coil
Similar to a bar-magnet outside the coil
Note: You can use the Right Hand Grip rule to show the direction of flux inside a solenoid, if your fingers indicate the direction of current

5. Flemings Left Hand Rule
Field
Current
Thrust (Force)
Thumb
First
Centre

6. Force on a Current Carrying Wire in a magnetic field
The Magnetic Field from a current carrying wire will interact with a magnetic field from a magnet and create a force.
in a direction perpendicular to B and I
Force on this part of the wire B I l
When the field is parallel to the current there is no force.

7. Questions: Page 231, Questions 8,10, 12 and 13
Extension Page 277 Q17 & 16
Note: By convention, a vector property (Field, Current or Force) going into the page is represented by a A vector field coming out of the page is represented by a

8. A coil is set up in a magnetic field as shown. The distance AB = 0
A coil is set up in a magnetic field as shown. The distance AB = 0.15m and the distance BC = 0.1m.
Magnetic Flux Density, B = 0.5mT and the current going through the coil is 3A.
Calculate the force vectors on the sections AB, BC and CD
Calculate the torque on the coil.
If the coil rotates through 90o so that AB is at the back and CD is at the front, calculate the force vectors on the sections AB, BC and CD
Determine what torque will be produced by these forces around the axis.
If the coil rotates through 180o with the current still flowing round the coil ABCD, what will happen to the torque?
If the coil is replaced by a coil with 50 turns, each insulated from each other, rather than a single turn, what will happen to the torque?