Finding efficiency between transformers.

[Crusaderking1]

Ok, I have a primary and secondary coil. I set up a transformer between them. Each has 400 turns of coil(N). The primary coil produces a potential difference of 2.988 V. The secondary coil has a potential difference of 0.0551 V.

For the efficiency, I used the equation (Np*Vs)/(Ns*Vp) * 100%

Np-turns of primary coil(400)
Vs- potential difference of secondary coil(0.0551)
Ns- turns of secondary coil(400)
Vp-potential difference of primary coil(2.988)

When I plug them in, I get 1.84% efficiency.

Am I messing the formula up, plugging in the wrong values. etc?
1.84% seems awfully low.
Thanks.

 

[Redbelly98]

For equal number of turns on the primary and secondary, a 100% efficient transformer would have equal voltages on the primary and secondary. But the problem statement does give an awfully low value for the secondary voltage, namely 1.84% of the primary voltage.

Perhaps if you can you post the question in its exact wording, I can see if there is something we are missing.

 

[Crusaderking1]

This was a lab experiment, and these values were measured or given. the two coils were set up with an iron core and were faced toward each other with 2 voltage probes acting as a voltmeter.

Later on for a separate trial, we had the iron core placed right through the transformer with still two 400 coils, and then I calculated a reasonable 60.4% efficiency using the same formula as earlier.

I'm guessing that its a possibility that the more O-shaped iron core involved, the more efficient the transformer was, and that having no O-shaped iron core made it extremely, yet unbelievably, inefficient.

 

[Redbelly98]

Okay, it makes more sense now. Without the iron core in place, the coils are not coupled as strongly to one another.