Electromagnetic Induction
by Boss Magneto
1. A = area of surface
2. The induced emf, E, in any closed circuit is equal to the time rate of change of the magnetic flux through the circuit
3. Faraday's Law
3.1. E <>< d/dt x (Nϕ)
3.2. Middle Finger - Induced Current Direction
3.2.1. Father
3.2.2. Child
4. Unit: Wb (Weber)
5. Fleming's Right Hand Rule
5.1. Thumb - Force Direction
5.2. B = magnetic flux density
6. induced emf as B parallel plane of disc and axis of rotation
7. .
8. .
9. Index - Magnetic Field Direction
10. θ = angle between the magnetic field and the surface S
11. Units of E: V (Volts of induced current)
12. EMF induced in Moving Straight Conductor
12.1. E = Blv
12.1.1. v = velocity
12.2. E = 0, when l or v is parallel to B
13. Use of search coil to measure B
14. .
14.1. where f = 1 / T
14.1.1. T = Period of revolution
14.2. AC Generator
14.2.1. Φ = NBAcosθ
14.3. .
15. BUT, θ = ωt
15.1. Hence, Φ = NBAcos ωt
16. l = length of conductor
17. Applications of EMI
17.1. Use of search coil to measure flux density
17.2. Disc Generator
17.2.1. E = Bπr²f
17.3. Eddy Currents
17.3.1. Magnetic Effect
17.3.1.1. can be reduced by creating slots in the plate
17.3.1.1.1. Eddy currents cannot pass through air gaps
17.3.1.2. Follow Lenz Law
17.3.1.2.1. oppose the motion producing them
17.3.2. Heating Effect
17.3.2.1. coil carrying high frequency ac, causes rapidly changing magnetic flux to induce large eddy currents
18. Currents that are caused in metals moving in a magnetic field
18.1. can be +ve or -ve
19. Q = NBA / R
19.1. R = total resistance of circuit
20. Magnetic flux ϕ
21. ∆Q = ∆Φ / R
22. Lenz's Law
22.1. E = - dϕ / dt
22.1.1. E = - N d(BAcosθ) / dt
22.1.2. Unit: V (Volts)