A lightweight horizontal aluminium rod forms one side of a rectangular frame used in…
MATHEMATICS · Multi-part · A Level · Mathematics · Forces and Newton's laws · Forces and Newton's laws
Problem
A lightweight horizontal aluminium rod forms one side of a rectangular frame used in a laboratory balance. The rod is 0.30 m long and is positioned at right angles to a uniform magnetic field that acts vertically. A hanger attached to the rod exerts a downward load of 1.2 N when in use. The power supply connected to the frame can safely deliver a current of up to 20 A.
Answer the following questions using g=10ms−2 wherever needed.
(i) Calculate the minimum magnetic field strength required so that the magnetic force on the rod exactly balances the 1.2 N load.
(ii) If the laboratory electromagnet available can provide a maximum field of 0.25 T only, state with calculation whether the present design is feasible.
(iii) Suggest ONE design change (other than increasing the current beyond 20 A) that would allow the balance to work with the same 0.25 T field, and justify your suggestion with suitable reasoning or calculation.