 # Step-up and step-down transformers

What are step-up transformers and step-down transformers? It is easy to remember by visualising the following diagrams:   A step-up transformer has more turns on the secondary coil than the primary coil.

To work out what impact this has on voltage or current, rather than remember what the impact is, Mammoth Memory suggests that you try some basic numbers into the formulas you have learnt. It is easier than remembering the results.

The impact of a step-up transformer on voltage can be very quickly worked out by using:

V_1/V_2=N_1/N_2

Plug some imaginary numbers in.

(15\ \v\o\l\t\s)/V_2=(10\ \turns)/(100\ \turns)

V_2=(15xx100)/10

V_2=150\ \v\o\l\t\s

STEP-UP IS AN INCREASE IN VOLTAGE

The impact of this on current can be very quickly worked out by using:

V_1\ \I_1=V_2\ \I_2

Using

V_1=15\ \v\o\l\t\s  and V_2=150\ \v\o\l\t\s

and an imaginary current of 5 amps for I_1

We get:

15xx5=150xxI_2

I_2=(15xx5)/150

I_2=0.5\ \amps

STEP-UP IS A DECREASE IN CURRENT

: A step-down transformer has fewer turns on the secondary coil than the primary coil.

The impact of this on voltage can be very quickly worked out by using:

V_1/V_2=N_1/N_2

Plug some imaginary numbers in.

(150\ \v\o\l\t\s)/V_2=(100\ \turns)/(10\ \turns)

V_2=(150xx10)/100

V_2=15\ \v\o\l\t\s

STEP-DOWN IS A DECREASE IN VOLTAGE

The impact of this on current can be very quickly worked out by using:

V_1\ \I_1=V_2\ \I_2

Using

V_1=150\ \v\o\l\t\s  and V_2=15\ \v\o\l\t\s

and an imaginary current of 5 amps for I_1

5xx150=15xxI_2

I_2=(5xx150)/15

I_2=50\ \amps

STEP-DOWN IS AN INCREASE IN CURRENT

## Conclusion

A step-up transformer increases voltage.

That is, the voltage at the secondary coil is more than the voltage of the primary coil. Although the voltage increases, the current is reduced.

A step-down transformer does the opposite.