# Transformer – energy cannot be lost or gained

Now we know that doubling the coils doubles the voltage and therefore:

V_1/V_2=(Number\ \turns\ \1)/(Number\ \ turns\ \2)

We must also remember that:

Power can not be lost or gained

If Power=VI and power can not be lost or gained it follows that if voltage is increased, current is reduced and vice versa. Remember:

V\o\l\t\a\g\e\ \1xxCurrent\ \1=Primary\ \Power=S\e\c\o\n\d\a\r\y\ \Power=V\o\l\t\a\g\e\ \2xxCurrent\ \2

(NOTE: Secondary power is slightly less due to small inefficiencies, but they are ignored here)

This is an easy way for you to remember that:

 V_1xxI_1=V_2xxI_2

 1000 v and 1 Amp equals 1000 watts 1 volt and 1000 Amps equals 1000 watts 500 v and 2 Amps equals 1000 watts 5 v and 200 Amps equals 1000 watts

Therefore because

 V_1I_1=V_2I_2

 V_1/V_2=I_2/I_1