1. Magnetism 1

2. Magnetism unlike poles attract a broken magnet creates new poles
Magnetism = attraction or repulsion due to the arrangement of electrons
like poles repel
unlike poles attract
a broken magnet creates new poles

3. Magnetic Field Magnetic Field
area around a magnet where magnetic forces are detected
field lines show direction of field (NS)‏

4. Use of Magnetism 1

5. Electromagnet Electromagnet
strong, temporary magnet formed when current is passed through a coil of wire surrounding an iron core
acts like a bar magnet when current is on

6. electromagnet rotates between the poles of a fixed magnet Poles on
C. Motor
Motor
electrical energy  mechanical energy
electromagnet rotates between the poles
of a fixed magnet Poles on
electromagnet switch in intervals
making it spin

7. Creating Electricity 1

8. Electric Generator Electric Generator
mechanical energy  electrical energy
armature is rotated between magnet poles
magnetic field induces a current in the wire coil

9. DC & AC Alternating Current (AC)‏
Direct Current (DC)‏
current flows in one direction
dry cells
Alternating Current (AC)‏
current reverses its direction at regular intervals
electrical outlets

10. Transformer Transformer increases or decreases AC voltage
primary coil AC produces a magnetic field that induces AC in the secondary coil
voltage ratio = ratio of turns in each coil

11. D. Transformer Step-down Transformer Step-up Transformer
increases the voltage
more turns
power plants
Step-down Transformer
decreases the voltage
fewer turns
household appliances
(hairdryers, etc.)‏

12. Transformer Equation
Is = Vp = Np Ip = Vs = Ns Primary Coil (p) – where the initial electrical current comes into the transformer Secondary Coil (s) – where the electricity leaves the transformer N - Number of turns in the coil

13. Transformers Step–up Transformer Vp < Vs Ip > Is Np < Ns
Step-Down Transformer Vp > Vs Ip < Is Np > Ns

14. Example Problem
A step-up transformer has a primary coil consisting of 200 turns and a secondary coil consisting of 3000 turns. The primary coil is supplied by an effective AC voltage of 90.0 V.
What is the voltage in the secondary circuit?
The current in the secondary circuit is 2.0 A. What is the current in the primary coil?

15. Example Continued Np = 200; Ns = 3000; Vp = 90.0 V; Is = 2.0 A
Solve for Vs
(Vs/Vp) = (Ns/Np)  (Vs/90) = (3000/200)
Vs/90 =  Vs = 90 x 15 = 1350 V

16. Example Continued 2.0 / Ip = (90 / 1350)
2.0 / Ip = (multiply Ip out of denominator)
2.0 = x Ip (divide by )
2.0 / = Ip = 30 A