Variation of Current in Step up and Step down Transformer
The terms “current change” in the context of transformers refer to the variation in current magnitude between the primary (input) and secondary (output) coils of a transformer. Transformers work on the principle of electromagnetic induction and can either increase (step-up) or decrease (step-down) voltage. Due to the conservation of energy (ignoring minor losses), as the voltage is stepped up, the current is stepped down and vice versa.
1. **Step-Up Transformer**: In this type of transformer, the voltage is increased from the primary coil to the secondary coil. As a result, the current in the secondary coil (output side) is less than the current in the primary coil (input side). This is because the power on both sides remains roughly equal (ignoring losses).
If 
is the voltage and 
is the current on the primary side, and 
is the voltage and 
is the current on the secondary side, then for a step-up transformer:
and because 
(power in the primary) and 
(power in the secondary) and 
, then:
2. **Step-Down Transformer**: In this type of transformer, the voltage is decreased from the primary coil to the secondary coil. Consequently, the current in the secondary coil (output side) is greater than the current in the primary coil (input side).
Using the same notation as above for a step-down transformer:
and because and and , then:
It’s essential to keep in mind that while transformers can change the voltage and current levels, they cannot alter the power significantly (with minor changes due to losses). In other words, transformers are not power-generating devices; they merely change the levels of voltage and current.