Magnetic flux density and magnetic forcesEdexcel International A Level Physics: Mind map

Exam questions on Magnetic flux density and magnetic forces

1. A proton (charge +1.60 × 10⁻¹⁹ C) moves at 2.0 × 10⁶ m s⁻¹ and enters a region of uniform magnetic field of flux density 0.40 T. Its velocity is perpendicular to the field direction.
   Explain why the proton follows a circular path in the field while its kinetic energy stays constant.2 marks
2. A circular coil of 150 turns and radius 2.0 cm is placed in a uniform magnetic field of flux density 0.30 T. In its starting position the plane of the coil is perpendicular to the field lines.
   State what is meant by flux linkage and explain why the flux linkage is zero when the plane of the coil is parallel to the field.2 marks
3. A straight horizontal copper wire of length 0.12 m and mass 3.0 g carries a current of 8.5 A in a uniform horizontal magnetic field of flux density 0.25 T. The field is directed due north and the current flows due east, so the wire is perpendicular to the field.
   Calculate the magnitude of the magnetic force on the wire, and the magnitude of the force if the wire were turned in the horizontal plane to make an angle of 30° with the field.3 marks