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How does a transformer work?

Transformer - Function

Transformer - Function

Viewing (ideal) unloaded transformer

By neglecting the losses, the following formulas can be derived:

For the unloaded transformer, i.e. no load connected:

N1  =   N2            (1)
V1       V2

We verify our assertion with the values from the video:

V2 =   N2  *  V1  =  300  *  100 V  =  25 V
.           N1                  1200

Loaded ideal transformer:

When a load is connected, the output voltage V2 can and will drop. How much it drops depends on the load (output current I2) and how the transformer is designed.

If losses are neglected, however, the output power is equal to the input power:

.           P1              =    P2

=>       U1  *  I1   =   U2  *  I2       (2)

Eq. (1) in eq. (2) shows the relationship between current and number of windings:

I2 =   N1   * I1
.         N2