A. Frequency
B. Mutual Flux
C. Load current
D. Applied Voltage
Answer: C. Load current
Explanation:
Leakage flux:- The flux that escapes from the core and flux that passes through one winding only.
The flux that links with the primary, but not with the secondary, is known as primary leakage flux, while that which links with the secondary, but not the primary- winding is called the secondary leakage flux.
The value of leakage flux is proportional to the load on the transformer.
Since each leakage flux is linked with one winding only, it induces back e.m.f. in that winding, which opposes the current flow in the winding.
The greater the leakage flux, the greater the voltage drop. Good transformer design aims to reduce the leakage flux to a low level.
The voltage drop caused by leakage flux is proportional to the load current.
The greater the load current, the greater the magnitudes of both the primary and secondary ampere-turns, and hence the greater the respective leakage fluxes in both primary and secondary windings.
Although leakage flux has an adverse effect on the transformer output voltage, it proves an asset under severe short-circuit conditions; the large voltage drop caused by the intense leakage flux limits the current to a lower value than would otherwise occur if no leakage were present and thus helps to avoid damage to the transformer.
In a Transformer, Core flux is the difference between primary flux and Secondary flux which are opposite to each other in direction.
When Current increases due to increased load (and voltage remains the same).
Then both primary and secondary flux increase. Because both of them increase, so their difference remains the same. And all remaining flux is forced out.
Hence leakage flux increases with current, but Core flux remains constant.