Resistor combinations, Kirchhoff's rules worked with a stated sign convention on two circuits, Wheatstone and metre bridges with end error, the potentiometer null method, and both galvanometer conversions.
Unit 4 carries 9 of the 50 physics marks, the largest single block in the paper; with seven chapters sharing them, this one averages a little over one (MEC publishes weights by unit, not by chapter). It is the densest chapter in the unit — three scope points, four named instruments and two conversions — and it is also the most mechanical. Kirchhoff's rules are not a topic to understand once and hope; they are a procedure with signs, and a student who writes the loop equations the same way every time will never get them wrong.
The MEC scope lines are: Kirchhoff's laws and combinations of resistors; Wheatstone bridge, metre bridge and potentiometer; Galvanometer as ammeter and voltmeter. The three headings below are those points, in MEC's order. The ideas the chapter leans on — Ohm's law, emf against terminal pd, internal resistance — are in Electrical quantities.
Upgrade to unlock this and every premium study note, formula sheet and high-yield summary — plus unlimited mocks and full solutions.
See the plansCurrent Electricity and Magnetism: Unit Map and Reading Order
What the Current electricity and magnetism unit covers, how many of the 50 Physics questions it carries, and the order to read its seven chapter notes in.
Physics Formula Sheet — Rapid Revision
Every Physics relation on the MECEE-BL blueprint on one page: mechanics, heat, waves and optics, electricity and magnetism, modern physics — with the constants and unit traps that cost marks.
Physical Quantities, Vectors and Scalars: Units, Errors, Resultants
SI units and prefixes, precision against accuracy, significant-figure arithmetic, error combination, the dimensional formulae that get asked, and every vector law from the parallelogram to the river crossing.
Kinematics: Motion Graphs, Free Fall and the Projectile
The three equations of motion, what every slope and area on a motion graph means, free-fall and relative-motion numericals, the full projectile set, and what air resistance does to all of it.