A transformer is a device that is used to convert high voltage ac at low current to low voltage ac at high current and vice versa. Step-up transformer converts low voltage ac to high voltage ac. Step down transformer converts high voltage ac to low voltage ac.Construction: The schematic diagram of a transformer is given in Figure 1. Two coils named P (primary) and S (secondary) are wound the laminated iron core. An iron core is made up of large no. of rectangular iron strips insulated from each other which is grouped together to form a single block. Input ac supply is provided to the primary coil (P) while output ac is obtained from the secondary coil (S).
Principle: A transfer works on the principle of “Mutual Induction”. An alternating current of ac is responsible for the continuous change of magnetic flux in the neighboring coil which finally provides induced emf in the coil.
When ac of certain emf (εP) is connected to the primary coil (P), due to periodical change of current in it, magnetic flux linked to the secondary coil (S) continuously changes and hence induced alternating emf (εS) is produced in the secondary coil. Here, the soft iron core is used as a core, for it enhances the linking of flux produced by the primary coil to the secondary coil. Assuming no magnetic flux leakage, here rate of change of magnetic flux (dΦ/dt)for the primary and secondary coils will be the same.
The efficiency of a Transformer:
In general, no transformer is loss-free. i.e. there is always a loss of some energy in primary and secondary coils and hence the power of secondary coil is not equal to the primary coil.
The greater is the power transferred to the secondary coil, better is the performance of the transformer.
Thus, the efficiency of a transformer is defined as the ratio of output power to input power. Symbolically,
Also see (Click on these quick links) :
1. Domain Theory of Ferromagnetism: http://www.askmattrab.com/notes/93-domain-theory-of-ferromagnetism
2. Antiferromagnetic and Ferrimagnet: http://www.askmattrab.com/notes/94-antiferromagnet-and-ferrimagnet
3. Magnetic Materials: http://www.askmattrab.com/notes/95-magnetic-materials
4. Working of the Transformer: http://www.askmattrab.com/notes/97-working-of-the-transformer