This how it works covers Why a Current-Carrying Wire in a Field Experiences a Force within The Motor Effect for GCSE Physics. Revise The Motor Effect in Magnetism for GCSE Physics with 19 exam-style questions and 12 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 5 of 12 in this topic. Use this how it works to connect the idea to the wider topic before moving on to questions and flashcards.
⚙️ Why a Current-Carrying Wire in a Field Experiences a Force
When current flows through a wire, it creates its own circular magnetic field around the wire. When this is placed inside an external magnetic field (e.g. between the poles of a magnet), the two fields interact.
On one side of the wire, the two fields point in the same direction and REINFORCE each other — creating a stronger field. On the other side, they point in opposite directions and CANCEL — creating a weaker field.
This asymmetry — strong field on one side, weak on the other — creates a net force pushing the wire from the stronger-field side toward the weaker-field side.
Catapult analogy: Imagine the magnetic field as a stretched elastic sheet. On the strong side, the field is "compressed" between the two sources — it pushes the wire out like a catapult. This is why the motor effect is sometimes called the "catapult effect".
Practice questions for The Motor Effect
What is the motor effect?
Explain how Fleming's left-hand rule is used to find the direction of the force on a current-carrying conductor in a magnetic field.