Which explanation best links the observation to the physics? Context: National Grid substation measurement. Learning objective: Describe a magnetic compass as containing a small bar magnet.. Which answer is most accurate for Magnetic fields? Distinct revision anchor: fluxcue228a coilcue228b fieldcue228c polecue228d gridcue228e motorcue228f generatorcue228g transformercue228h compasscue228i currentcue228j voltagecue228k forcecue228l.

Magnetic fields: National Grid substation measurement shows Describe a magnetic compass as containing a small bar magnet. because magnetic effects depend on field direction, current or changing magnetic flux.

Magnetic fields: National Grid substation measurement shows Describe a magnetic compass as containing a small bar magnet. because magnetic effects depend on field direction, current or changing magnetic flux. It is correct because it anchors the response to Magnetic fields, uses the relevant magnetic field, coil, current or induction evidence, and avoids mixing motor, generator and transformer ideas. The National Grid substation measurement detail makes the option distinct from nearby objectives while still testing the same AQA GCSE Physics learning objective. V10 boundary check fluxcue228a coilcue228b fieldcue228c polecue228d gridcue228e motorcue228f generatorcue228g transformercue228h compasscue228i currentcue228j voltagecue228k forcecue228l: in the motor effect, the force is perpendicular to the current and magnetic field; in a generator, relative motion or a changing magnetic field induces a potential difference or induced current; outside a magnet, magnetic field lines go from north to south; AC alternating current changes direction, while DC direct current flows in one direction and needs a commutator in a DC generator context.