# Why current is inversely proportional to voltage in transformer

FAQ | Mar 11,2023

In a transformer, the current in the secondary coil is inversely proportional to the voltage applied to the primary coil, according to the transformer equation:

Vp / Vs = Np / Ns

where Vp is the voltage applied to the primary coil, Vs is the voltage induced in the secondary coil, Np is the number of turns in the primary coil, and Ns is the number of turns in the secondary coil.

The equation shows that if the voltage applied to the primary coil is increased, the voltage induced in the secondary coil will increase proportionally, but the current in the secondary coil will decrease proportionally. This is because the power input to the transformer must be equal to the power output, neglecting losses. As power is the product of voltage and current, if the voltage increases, the current must decrease in order to maintain the same level of power output. Similarly, if the voltage applied to the primary coil is decreased, the voltage induced in the secondary coil will also decrease proportionally, but the current in the secondary coil will increase proportionally.

This inverse relationship between voltage and current in a transformer is a consequence of the law of conservation of energy, which states that energy cannot be created or destroyed, only transformed from one form to another. In a transformer, the electrical energy in the primary coil is transformed into magnetic energy in the core of the transformer, and then back into electrical energy in the secondary coil. The transformer equation ensures that the power input and output are equal, so that energy is conserved throughout the transformation process.

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