velox said:
Couple of revision questions:
Why does adding an iron core increase efficiency of a transformer?
And
Explain why voltage transformations are related to conservation of energy.
Thanks
1. Adding an iron core magnifies the magnetic field produced from the AC supply. Like when you add an iron core to solenoid, it increases its effect. Also if the iron core is laminated, it will reduce eddy currents and thus heat lost to suroundings will be minimised.... [thats my best guess]
2. Voltage transformations are related to the conservation of energy but the following equations VpIp = VsIs (where V= voltage, I =current , P = prim. s= second.)
Since Power is equal to P=VI , Voltage and Current are related in the first equation. If you have an increase in voltage (but transformers have the same power), then according to the second equation, P=VI, the current must come drop. If the current were to stay the same (or increase) whilst voltage were increase, then energy would be created and that would violate the Conservation of Energy.
E.g.
Transformer has input Power of say 10 watts
its voltage is 5V and currents is 2A Hence P=VI 10= 5x2.
Ideally, a perfect transformer has no power loss, hence 10 watts output. But say this was a step up transformer, to say 8V, then to obey the conservation of energy, the current needs to decrease. P=VI 10=8x1.25
hope that helps
