Flux and Induced Voltage

Decreasing Flux Flips Polarity

When flux decreases instead of increases, the induced-voltage magnitude can match while the polarity label flips to oppose the change. The 4 V result is exact for this ideal finite-change ledger; real polarity observations depend on coil orientation, sign convention, resistance, waveform timing, instrument leads, and measurement uncertainty.

The same magnitude with decreasing flux gets the opposite finite polarity. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Decreasing flux has the same magnitude case

Flux changes from 14 to 2 webers, so the magnitude of change is 12 webers.

∣ΔΦ∣=12 Wb|\Delta\Phi|=12\ \mathrm{Wb}
Induced emfChanging source-bound flux sets voltage.B=7 TA=2 m^2Phi=14 WbB=1 TA=2 m^2Phi=2 WbV=4 Vopposes decrease

The finite polarity label flips

The voltage magnitude is still 4 volts, but the polarity label now opposes the decrease.

∣V∣=4 V|V|=4\ \mathrm{V}
Induced emfChanging source-bound flux sets voltage.B=7 TA=2 m^2Phi=14 WbB=1 TA=2 m^2Phi=2 WbV=4 Vopposes decrease