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Asked in GSEB Board March 2023 · Force on a wire in a field
Idea: magnetic induction B is fixed by the force law F=BIℓ sin θ and by the flux relation Φ=BA, so every unit of B must follow from one of them.
From B=F/(Iℓ): the unit is newton per (ampere × metre), and this combination is given the name tesla.
From B=Φ/A: the unit is weber per square metre, the same thing.
Newton-metre per ampere is N m A⁻¹=(N/(A m))×m², that is tesla × area — the weber, which measures magnetic flux, not magnetic induction.
So newton-metre per ampere is not a unit of magnetic induction.
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