I see you've uploaded an image of an exam paper from Yaba College of Technology's School of Engineering, focusing on Electrical Machines II. Here’s a quick breakdown of the questions as listed in your image:

1. Question 1:

   • (a) Discuss the principle of operation of transformers.
   • (b) Given the equation $E_s = 4.44N_s\Phi f$, show that $E_s/E_p = N_s/N_p$ (related to transformer universal equation).
   • (c) A single-phase transformer has 500 primary turns and 1200 secondary turns, with a primary voltage of 500 V. If the flux density is 1.5 Wb/m² and the core area is 50 cm²:
     1. Calculate the value of flux density in the core.
     2. Calculate the secondary voltage.

2. Question 2:

   • (a) Define terms related to electromagnetic induction: magnetic flux, flux linkage, etc.
   • (b) In a laboratory experiment to verify Faraday’s law, a coil is rotated, and the induced e.m.f. over an interval is recorded. Calculate:
     1. Magnetic flux.
     2. Average current.

3. Question 3:

   • (a) Define self-inductance and explain mutual inductance.
   • (b) Given a transformer and several impedances, calculate:
     1. Equivalent resistance as referred to primary.
     2. Equivalent resistance as referred to secondary.
     3. Equivalent reactance as referred to both primary and secondary.

4. Question 4:

   • (a) Draw a well-labeled electrical machine classification chart.
   • (b) Prove the energy stored in the magnetic field of a coil using the given relationship.
   • (c) State three advantages of 3-phase transformers over single-phase transformers.

Would you like a detailed explanation or step-by-step solution for any of these specific questions? Let me know if you need assistance with calculations or theory!

Here are five related questions for deeper understanding:

1. What are the main losses in a transformer and how can they be minimized?
2. How does the core material affect transformer efficiency?
3. How does mutual inductance differ from self-inductance in transformers?
4. Can you explain the relationship between voltage, current, and flux in an ideal transformer?
5. What is the significance of phase grouping in three-phase transformers?

Tip: When calculating transformer efficiency, always account for copper and iron losses to get an accurate result.