Electric and magnetic fields

Question 1

13. Explain why the magnitude of the magnetic flux through the coil varies as the coil rotates (2 marks).

Answer 1

• The component of B perpendicular to the area changes

* Depends on cosθ

Question 2

14. The primary coil in a transformer is connected to an alternating voltage supply. Explain how an e.m.f. is induced in the secondary coil (3 marks).

Answer 2

• A changing magnetic flux is produced in the primary coil
• The iron core links this magnetic flux to the secondary coils
• The changing magnetic flux through secondary induces an emf in the secondary coils.