websites just say "Because of faradays law"........ I don't get it, i want to know why, so I can quote it in my report. thankyou for reading.
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A back emf is an induced emf .. and Faraday's law enables a calculation for an induced emf (E) ..
"Induced emf = (-) rate of change of magnetic flux-linkage with the moving conductor"
Magnetic flux-linkage is the product of the field strength (B, Tesla) x Area of the field swept by the moving conductor(s) (A, m²) x number of circuits (N coils) sweeping the field.
ie .. Flux-linkage = B.A.N .. (unit Weber, Wb)
The emf (= rate of change of flux-linkage) is caused in this case by the changing area sweep rate (dA/dt, m²/s)
Hence .. emf E = (-) N.B.dA/dt .. Volts (neg sign indicating back emf)
► so the faster the conductor(s) move the greater the area swept per second (dA/dt) .. and the greater the back emf will be.
"Induced emf = (-) rate of change of magnetic flux-linkage with the moving conductor"
Magnetic flux-linkage is the product of the field strength (B, Tesla) x Area of the field swept by the moving conductor(s) (A, m²) x number of circuits (N coils) sweeping the field.
ie .. Flux-linkage = B.A.N .. (unit Weber, Wb)
The emf (= rate of change of flux-linkage) is caused in this case by the changing area sweep rate (dA/dt, m²/s)
Hence .. emf E = (-) N.B.dA/dt .. Volts (neg sign indicating back emf)
► so the faster the conductor(s) move the greater the area swept per second (dA/dt) .. and the greater the back emf will be.
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Voltage is proportional to the rate of change of magnetic field. The amount of change in the magnetic field is the same regardless of speed. It goes from full magnitude in one direction to full magnitude in the other direction. So if you do it in less time because you complete a revolution in less time, then the rate of change is higher.