Electrical Engineering - Transformers - Discussion

@Anand

Formula for step up and step down transformer is same only.
that is given by,
Transformer ratio ====> K=N1/N2=V1/V2=I2/I1-------(1).

Now this question will be raise in your mind that how this formula came. So here it is:

we know that Energy(power) cannot be created and destroyed but it can be transfer from one form/primary side to other form/secondary side.
So Power P=VI
Then in transformer===> V1*I1=V2*I2.

=> V1/V2=I2/I1 = K(let it be)-----(2).

And also we know that,
In a transformer, Volts per Turn coil is constant on both sides.
So=> V1/N1=V2/N2.

=> V1/V2=N1/N2 = K (from (2))-----(3).

Compare 2 and 3.

Transformer ratio K = V1/V2=N1/N2=I2/I1.

@Anu.

Here N1:N2 is 15:1 and V1:V2 is 110:V2.

Here N1<N2 clearly shows that no.of turns at secondary side of transformer is less than primary turns of the transformer which shows that it is a step down transformer.

So V2 should be less than V1=110 Volts.

And also we know that,

Transformer ratio, N1/N2=V1/V2=I2/I1=k.

So from above take only N and V.

So N1/N2=V1/V2.

=>15/1 =110/V2.

=>V2=110/15.

=>V2=7.33333 Volts.

Hope all of you agree this one.

Given Data:

1. Primary Voltage: 110V.
2. Turns ratio: 15:1 (15=Primary turns, 1=Secondary Turns).

V1/V2 = N1/N2.
110/V2 = 15/1.
110*1/ 15 = V2.
Hence V2 = 7.3V across transformer secondary winding.

Now, load is of 120Ohm connected across the secondary winding.

So, the load will face the same secondary voltage.

See here the most confusing part is TURN RATIO. Which is a per my knowledge is N2/N1. As it is used in earlier question of this quiz. As per this ratio the answer is 1650. I do not know why people are saying that since the answer 1650 is not there so they are using another formula which is reverse of this.

Since V2/V1 + N2/N1

In the ques, N2/N1 can b either 15: 1 or i: 15 depending on the type of transformer ( step up or step down)

If it is step up it is 15 : 1 &, if it is step down, it is 1 : 15

Solve 4 both values to get V2 and look at the options whch value of V2 falls correct.

Have a nice day !

Hello guys,

For step down transformer, turn ratio > 1.

For step down transformer, turn ratio < 1.

Here turn ratio is 15, that means greater than 1 then we can say that this is a step down transformer.

So O/P will be less than 110 volt and formula will be Np/Ns = 15/1.

Here, Turns ratio with Primary is 15:1, So, I take it as N1=15, N2=1.

Normally, Turns ratio formula will be N2/N1.Some times it change accordingly with the question.

v1/v2 = n1/n2
110/v2 = 15/1
v2 = 110/15
v2 = 7.3V(Step down Xr).

But why they gave load resistance value?

@Imran

Given value N1:N2 = 15 : 1 (That is N1 = 15, N2 = 1)

Turns ratio = (N1/N2) = 15/1 (ratio > 1 ; Step down transformer).

As you said, V2/V1 = N2/N1

V2/110v = 1/15

V2 = 110v/15

V2 = 7.3333... volts.

Hope this will help to clear your doubts. Have a nice day!

Given value N1:N2 = 15 : 1 (That is N1 = 15, N2 = 1).

Turns ratio = (N1/N2) = 15/1 (ratio > 1 ; Step down transformer).

As you said, V2/V1 = N2/N1.

V2/110v = 1/15.

V2 = 110v/15.

V2 = 7.3333... volts.

Hope this will help to clear your doubts. Have a nice day!

We know k = n2/n1.

And here 15:1 is given,
Therefore k = 15:1.

Or n2/n1 = 15/1 = v2/v1.

So we get v2 = (n2/n1)*v1,

= (15/1)*110 = 1650v answer.

But there is no option. Therefore we go on this way,

n1:n2 = 15:1.

We get v2 = 7.333 v.