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Electric Transformer

Q. What do you mean by mutual induction? → It is the process of producing electric current on coil by passing electric current to next coil nealy placed. Q. What is the transformer? On which princile does it work? → The transformer is electric equipment which is used to increase or decrease the electromotive force (emf) of alternating current (AC). Thransformer is of two kinds : Step up trnsformer : Step down transformer: By the formula:- $\frac{\mathrm{V<sub>1</sub>}}{\mathrm{n<sub>1</sub>}}$ =$\frac{\mathrm{V<sub>2</sub>}}{\mathrm{n<sub>2</sub>}}$ Input power P1 = Output power P2 This implies, I1V1 = I2V2

Difference between Step up and Step down transformer
Step up transformer	Step down transformer
The transformer which is used to increase emf of ac current is called step up transformer	The transformer which is used to decrease emf of dc current is called step down transformer.
Secondary coil is greater than the primary coil i.e. n2 > n1	Primary coil is greater than secondary coil i.e. n1 > n2

Q. What is transformer core?
→ U shaped soft metalic sheets on which primary and secondary coils are rolled and also every sheet are leminated with Barnesh or Selaak to form like as single body.
Q. Without use of transformer use of uses of AC current is limited, clerify?
→ Transformer increase or decrease emf of AC current. Without use of transformer we can't convert AC as we required. So if not so use of AC will limited.
Q. Efficiency of transformer never 100%, why?
→ Due to resistance in coil of transformer, efficiency of it never 100%.
Q. Why core should leminated?
→ The eddy current on core produce heat on transformer. If there is excess of heat then trnsformer may burn and also low output. Therefor to minimise heat produced core are leminated.
Q. Transformer coil is leminated, why?
→ During the flow of current in coil eddy current produced in core. This eddy current produced heat which cause to burn or low out put. To minimise produce of eddy current coil are leminated.
Q. Transformer core are made of soft metal, why?
→ Soft metalic core increase the output on secondary coil and also it minimise destroy of current between primary and secondary coil. Therefor core made by soft metal.
Q. In transformer secondary coil and primary coil never equal, why?
→ Transformer use to increase or decrease the emf of AC. If primary and secondary coil is equal then input volt is equal to output volt. So primary coil and secondary coil never equal.
Q. Which function does the core in transformer?
→ Magnetic field developed in input side transformer core develop magnetic field in output side.


Numerical Problem

Q. In a transformer number of primary coil is 150 times the number of secondary coil. If 220 AC developed in a secondary coil then what is the primary volt? → According to question n1 =150 n2 $\frac{\mathrm{n<sub>1</sub>}}{\mathrm{n<sub>2</sub>}}$=150 Secondary voltage V2 = 220v Primary voltage V1 = ? By the formula:- $\frac{\mathrm{V<sub>1</sub>}}{\mathrm{n<sub>1</sub>}}$ =$\frac{\mathrm{V<sub>2</sub>}}{\mathrm{n<sub>2</sub>}}$ This imples, V1 = $\frac{\mathrm{V<sub>2</sub>}}{\mathrm{n<sub>2</sub>}}$. n1= V2.$\frac{\mathrm{n<sub>1</sub>}}{\mathrm{n<sub>2</sub>}}$ V1 = 220v × 150 =33000v

Q. Primary voltage 220v, then what is the secondary voltage? ( where, ratio of secondary to primary coil is 1/2). → Primary voltage V1 = 220v Ratio of secondary to primary coil $\frac{\mathrm{n<sub>2</sub>}}{\mathrm{n<sub>1</sub>}}$ = $\frac{1}{2}$ Secondary voltage V2 = ? By the formula:- $\frac{\mathrm{V<sub>1</sub>}}{\mathrm{n<sub>1</sub>}}$ =$\frac{\mathrm{V<sub>2</sub>}}{\mathrm{n<sub>2</sub>}}$ This imples, V2 = $\frac{\mathrm{V<sub>1</sub>}}{\mathrm{n<sub>1</sub>}}$ . n2 = V1. $\frac{\mathrm{n<sub>2</sub>}}{\mathrm{n<sub>1</sub>}}$ V2 = 220 × $\frac{1}{2}$ = 110v.