Transformers can be used for various applications they might serve any of the following functions:-
1. To decrease and increase current and voltages from one circuit to another as usually at Transmission end step up transformers are used as in step-up transformers current get reduced and which will leads to lower I2R losses. At distribution at step-down transformers are used as per voltage level required at distribution end.
2. Impedance Matching:-
Transformers can be used for impedance matching of load impedance with source impedance; this will be done to transfer maximum power at load.
3. Isolation of circuit:-
Transformers can also be used to isolate the particular circuit from another so that any faults in particular circuit could not get transferred to other circuit. They usually used to stop flow of dc while ac is permitted to flow to load, as DC could not get transferred in Transformer action.
4. Stepping Up the voltage
Transformers are used for stepping up the voltage where voltage is low and needed to be increased to higher levels
5. Stepping down the Voltage:-
Transformers are used to Stepping down the voltage i.e. where high voltages are available and voltage required of low level.
6.In electronics Circuits:-
Transformers are used in both in power and electronic circuits.
Transformers are used for AC only and can't be used for DC applications.
The reason behind that transformer work on the principle that current generate magnetic field in winding. More importantly is that change in magnetic flux induces voltage in secondary winding. But DC is constant so there will not be rotating field so voltage will not be induced in secondary winding, voltage will be induced as soon DC is switched on/off only.
You have often seen that there are gravels below transformer and around large Transformers, do you know what is the reason behind the same?
Answer for the same is that to prevent from snakes as large transformers produce very high vibrations due to magnetostriction which get transmitted to ground. Due to that effect Transformers attracts snakes. To avoid snakes gravels are placed transformers.
Magnetic field induced in Transformers inside is very high and ranges from 1.5 to 1.6 tesla, this magnetic field is very large in comparison to magnetic field strength of earth or sun.
Earth magnetic field is of the order of microtesla only and sun magnetic field range is from 0.1 -100 milli Tesla.