Magnetic Units, Dimensions, and Scaling Checks
Tesla satisfies 1 T = 1 N/(A m) = 1 Wb/m^2. Magnetic moment has unit A m^2, flux has unit Wb, and mu_0 has unit T m/A. Dimensional consistency is necessary but not sufficient for a correct formula.
Why this shows up in the exam
Checking numerical formulas · Selecting correct dimensional options · Converting gauss, tesla, centimetres, and micro-units
Learn the idea
Unit and dimension checks expose missing factors and distinguish field, flux, moment, and force. Magnetism formulas contain many similar symbols. Tracking SI units makes it harder to confuse tesla, weber, ampere metre squared, and newton per ampere metre.
🧠 Memory hook: Tesla is force per ampere-metre; weber is tesla-area.
Get this one clearly and it pays off every single time it shows up in the paper. 🎯
Formulas & facts to keep ready
- 1 T = 1 N/(A m) — tesla from force on a current element
- 1 Wb = 1 T m² — weber as magnetic flux unit
- [m_magnetic] = A m² — SI unit of magnetic dipole moment
- [mu₀] = T m/A — SI unit of vacuum permeability
How to approach it
- 1Convert every quantity to SI
- 2Check dimensions before arithmetic
- 3Then test geometry, sign, and limiting behavior
Common slip-ups that cost marks
- •Treating tesla and weber as interchangeable
- •Skipping centimetre or micro-prefix conversion
- •Assuming dimensional correctness proves physical correctness
🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.
Original chapter practice
Original questions for this chapter, not past-paper questions or an exact mapping to this individual concept.
A charge of 2 microC moves perpendicular to a 3 T magnetic field at 4 x 10^5 m/s. Find the magnetic force.
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