The voltage on both ends of a dry battery pack is 1.5 volts. If you want a higher voltage, you have to stack each battery in series. Each time you increase one bar, the voltage will increase by 1.5 volts. A change in the high or low voltage is possible through an increase or decrease in the number of battery packs. Can a transformer be used to raise the 1.5 volts voltage at both ends of the battery to the required voltage?
The answer is not possible since transformers can only be used to raise or lower alternating voltages; the battery current is direct current, always running from the battery’s anode to the cathode. The voltage formed at the ends of the battery is called the direct voltage.
To clarify this problem, we can do a little experiment. Use a paint-coated wire to wrap 50 turns on one end of a large iron nail, as the primary coil, and then on another winding with an equal number of turns as the secondary winding. It is a simple transformer. Connect the transformer’s secondary winding to the ammeter and the primary winding to the 1.5-volt battery. Based on the transformer’s principle, when in the primary winding with current flowing, there must also be current flowing in the secondary winding. However, the ammeter needle deviates only one when the battery is just circuited (or cut off), then quickly returns to its original stationary state. That said, in the secondary winding, there is no current flowing. Thereby, it can be seen that a transformer cannot use DC voltage to raise the voltage.
When passing through the primary winding of a transformer, DC will also generate a magnetic field around the primary winding. However, it is a type of d.c field with fixed poles. The magnetic field’s strength and direction are also unchanged, can not induce currents in the secondary winding, two ends of the secondary winding also cannot appear voltage.
Of course, we can still have a way for the transformer to raise or lower the DC voltage but have to go through a conversion. The way to do this is to first pass DC through the oscillating electronic circuit into alternating current, then use a transformer to increase or decrease the voltage, again to the AC through rectifier and filter wave, finally receive one-way electricity pressure is needed.