1. Combined Science (1-9): Electromagnetism The Motor Effect

2. Objectives:

3. Draw a line under last lesson’s work and write today’s title in your book...
Electromagnetism
28/11/2018
c/w

4. FLASHBACK
FLASHBACK: Define what is meant by a longitudinal wave and a transverse wave, providing an example of each

5. FLASHBACK- AFL

6. Explain how the strength of an electromagnet can be increased
Starter Activity
Explain how the strength of an electromagnet can be increased

7. This Force then would cause the wire to move
Explore:
The Motor Effect
The motor effect is the result of a wire that carries a current experiencing a force when it is placed between two magnets.
Task: To help remind ourselves, draw the magnetic field between two magnets
If we know the direction of the current and the poles of each magnet, we can determine the direction of Force.
This Force then would cause the wire to move

8. Explore: Fleming’s LEFT hand
This direction can be determined by using Fleming’s Left Hand Rule
If you position your fingers like that in the picture you’ll have the directions of each component
The thumb will show Force or Motion
The first finger shows the magnetic field
The seCond finger shows the current

9. Explore: Fleming’s LEFT hand
Keeping your fingers in that set position, orientate your hand so that the current finger is following the direction of current in the photo.
You’ll notice now that the other two (Field, B and Motion, M) now line up!

10. Which direction does the wire feel a Force?
Explore:
Fleming’s LEFT hand
Trial it with this one, notice this time the magnetic field is going directly upward and the current is going INTO the page.
Which direction does the wire feel a Force?

11. Explore:
Motor Effect
Use your knowledge of Fleming’s Left hand Rule to explain why this coil of wire will rotate when placed within a magnetic field

12. Calculating the force on the wire
The strength of the force (F) on a length of wire (l) which has a current (I) flowing through it whilst it is in a magnetic field (B) is given by the following equation:
𝑭=𝑩 ×𝑰×𝒍 × 𝒔𝒊𝒏∅
And assuming that the angle that the current makes with the magnetic field is 90° (perpendicular), this makes the equation simply:
𝑭=𝑩𝑰𝒍
So how can you make the motor move faster (more powerful)?
5.1 x N
You can speed up the motor by:
Increasing the current
Increasing the length of wire (number of turns)
Increasing the magnetic field

13. Calculating the force on the wire
𝑭=𝑩𝑰𝒍
A 200m long wire carries a current of 3A at right angles to the Earth’s magnetic field. There is a force of 0.024N on the wire. Calculate the strength of the Earth’s magnetic field (B)
B= F/IxL = / (3A x 200m) = N/Am
Write the answer in standard form
5.1 x N

14. Either side of the split rings are carbon brushes that exist to make electrical contact between the circuit and the motor.
The split ring commutator is split so that the current changes direction each half turn. This allows the coil to spin and it is this spin that makes the system a motor!

15. 6 mark question!
Explain how a coil of wire can be made to spin by using a pair of magnets, and a simple electrical circuit

16. 6 mark question!
Explain how a coil of wire can be made to spin by using a pair of magnets, and a simple electrical circuit
Attach the coil of wire to the simple circuit and place within the magnetic field between a North and South pole
Reference to Fleming’s Left Hand Rule
The wire with a flowing current will experience a force upon it
As each side of the coil of wire has an opposing direction of current, they receive Forces in opposite directions
This causes one side to be pushed upward and the other downward
This leads to rotation (spinning)

17. Objectives: