The class is about Electricity and Magnetism. The website wants exactly the perfect answer and in the same metric system units that are stated on the calculators that are on the picture for the question, if not, it'll mark it wrong.

Hall Effect Probe for Measuring Magnetic Field Strength In a probe that uses the Hall effect to measure magnetic fields, a 12.4-A current passes through a 1.3-cm-wide and 1.23-mm-thick strip of sodium metal. If the Hall emf is 2.42 uV, what is the magnitude of the magnetic field (take it perpendicular to the flat face of the strip)? Assume one free electron per atom of Na, and take its density to be 0.971 g/cm'. 5 IBI = T abc sin(x) Ox10 Submit Reset Reset All Draw a sketch. Set the electric force on a free charge equal to the magnetic force, and solve for B. .The current density j (current per cross-sectional area) is given by j = nev, where n is the number density of free charges, e is the charge of an electron, and v is the drift velocity of the electrons. See Chapter 25, Section 25-8, for more details. Note that j = I/A, where A is the area perpendicular to the current flow, so from I/A = nev, you can find the drift velocity v. See the Periodic Table in the back cover of your book to find out the atomic weight of sodium. .If you get stuck, see Example 27-10 for help