Higher Tier: Force Calculation and Direction
Part of The Motor Effect — GCSE Physics
This higher tier covers Higher Tier: Force Calculation and Direction within The Motor Effect for GCSE Physics. Revise The Motor Effect in Magnetism for GCSE Physics with 18 exam-style questions and 12 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 10 of 13 in this topic. This section is most useful once the core foundation idea is secure, because it adds the detail that pushes answers higher.
Topic position
Section 10 of 13
Practice
18 questions
Recall
12 flashcards
🎓 Higher Tier: Force Calculation and Direction
The force on a current-carrying conductor is given by F = BIL:
- F = force in Newtons (N)
- B = magnetic flux density in Tesla (T)
- I = current in Amperes (A)
- L = length of conductor in the field in metres (m)
This formula assumes the conductor is perpendicular to the field. If the conductor is at an angle θ to the field, the force becomes F = BIL sin(θ) — maximum at 90°, zero at 0°.
Worked example: A horizontal wire carrying 5 A lies in a vertical magnetic field of 0.4 T. The wire is 0.3 m long. Find the force: F = 0.4 × 5 × 0.3 = 0.6 N. Direction found using left-hand rule.
Motor torque: In a real motor, two sides of the coil experience equal but opposite forces — creating a turning effect (torque). More turns = more wire in the field = larger force = larger torque = faster or more powerful motor.