cameroon gce advanced level 2025 electrical machines 2

SECTION A: MAGNETIC AND ELECTROMAGNETISM

1. a) Figure 1 shows a flat coil of N numbers of Turns carrying a current I. If N=20 and R=2cm, calculate the flux density Bo, and the magnetic field strength H. (10 marks)

1. b) Figure 2 shows two straight conductors placed in a magnetic field, carrying currents I₁=15A and I₂=10A in the opposite direction and are separated by a distance of d=10cm from one another. Calculate the force exerted on one of the conductors (10 marks)

2. a) A straight conductor of length 5cm placed perpendicularly in a uniform magnetic field having a flux density of 0.8T is displaced at 0.1m/s. Calculate the electromotive force induced in the conductor (10 marks)

2. b) Calculate the average value of e.m.f. induced in an inductive circuit of inductance L=30mH when the current in the circuit varies from 0 to 5A in 0.1s (10 marks)

3. a) Calculate the magnetic field strength produced by a current of 50mA circulating in a coil of 300mm long and of 6000 turns. (10 marks)

3. b) A current of 100mA circulating in a coil of 500 turns, produces a magnetic flux of 50mWb

i. Calculate the inductance of the coil (5 marks)

ii. Calculate the energy stored in the coil (5 marks)