9702 · 20.1
Concept of a magnetic field — FAQ
Frequently asked questions for 9702 Concept of a magnetic field. Direct answers first, then deeper explanation — then practise with marking.
What is the key difference between magnetic flux density and magnetic flux?
Magnetic flux density (B) measures the strength of the magnetic field at a specific point, essentially how 'dense' the field lines are. Its unit is the Tesla (T). Magnetic flux (Φ), on the other hand, measures the total amount of magnetic field passing through a given area. Its unit is the Weber (Wb).
Why does an iron core increase the magnetic field of a solenoid so much?
Iron is a ferromagnetic material, meaning it can be easily magnetised. When placed inside a current-carrying solenoid, the iron core becomes strongly magnetised itself. Its own magnetic field aligns with and adds to the solenoid's field, significantly increasing the overall magnetic flux density.
Can electric fields and magnetic fields exist independently?
Yes, under static conditions. A stationary electric charge creates an electric field but no magnetic field. A steady current (charges moving at a constant velocity) creates a magnetic field. However, a changing electric field can induce a magnetic field, and a changing magnetic field can induce an electric field – this dynamic interplay is the foundation of electromagnetism and light waves.
What is the 'normal' to an area in the context of magnetic flux?
The 'normal' is an imaginary line drawn perpendicular to the surface of the area. When calculating magnetic flux with the formula Φ = BA cos(θ), the angle θ is always measured from this normal line to the direction of the magnetic field lines.