Correct Answer - Option 3 : A transformer cannot raise or lower the voltage.
Transformer:
- A transformer is a static (or stationary) piece of apparatus by means of which electric power in one circuit is transformed into electric power of the same frequency in another circuit.
- It can raise or lower the voltage in a circuit but with a corresponding decrease or increase in current.
- The physical basis of a transformer is mutual induction between two circuits linked by a common magnetic flux.
- In its simplest form, it consists of two inductive coils which are electrically separated but magnetically linked through a path of low reluctance.
- The two coils possess high mutual inductance. If one coil is connected to a source of alternating voltage, an alternating flux is set up in the laminated core, most of which is linked with the other coil in which it produces mutually-induced EMF (according to Faraday’s Laws of Electromagnetic Induction e = MdI/dt). If the second coil circuit is closed, a current flows in it and so electric energy is transferred (entirely magnetically) from the first coil to the second coil.
- The first coil, in which electric energy is fed from the AC supply mains is called primary winding, and the other from which energy is drawn out is called secondary winding.
In brief, a transformer is a device that:
1. A transformer is a device that transfers electric power from one circuit to another.
2. Transfers electric power from one circuit to another
3. It does so without a change of frequency
4. It accomplishes this by Faraday's law of electromagnetic induction and
5. Where the two electric circuits are in the mutual inductive influence of each other.
6. A transformer consists of 2 inductive coils.
7. The physical basis of a transformer is mutual induction between two circuits.
∴ The incorrect statement is 'a transformer cannot raise or lower the voltage', so the answer is option '3'.
