# Electrical Engineering - Transformers - Discussion

### Discussion :: Transformers - General Questions (Q.No.4)

4.

If a transformer has 50 turns in the primary winding and 10 turns in the secondary winding, what is the reflective resistance if the secondary load resistance is 250 ?

 [A]. 250 [B]. 25 [C]. 6,250 [D]. 62,500 Explanation:

No answer description available for this question.

 Bhagyashree said: (Dec 12, 2010) R2=250 k=n1/n2=50/10 R1=R2*k^2 =250*(2500/100) R1=6250ohm

 Hjhgjk said: (Dec 21, 2010) K=N2/N1 N1=50 N2=10 K=(10/50)=1/5 SECONDARY TO PRIMARY R/K^2 SO 250/(1/5)^2=250*25=6250 OHMS

 Prakash. D. said: (Feb 9, 2011) Turns ratio K= n1/n2= 50/10 K=5, w.k.t..., R1/R2=K^2 R1=250*25 R1=6250 ohms.

 Chintan said: (Apr 25, 2011) N1=50 , N2=10 Turn ratio K=N2/N1=10/50 K=1/5=0.2 now,R2/R1=K^2 R1=R2/K^2 =250/0.2^2 R1=6250 ohms.

 Siddu said: (May 30, 2011) Turns ratio will proportional to square of load then square of resistance in sec/pri 2n square.

 Pinnapareddy .Sandhya Lakshmi said: (Jun 27, 2011) r1=r2/k^2 k=n2/n1=10/50=1/5 r2=250 r1=250/(1/5)^2=6250 r1=6250

 Divij said: (Jun 29, 2011) r1=(n1/n2)^2*r2 WHERE n1=50 , n2=10,r2=250 Ans: 6250

 Sanjeev Kr. Rajoria said: (Sep 7, 2011) Transformation ratio a = N1/N2 so a=50/10=5 now load resistance referred to primary= (a^2)*(load resistance) so the reflected load = 5^2*250 = 25*250 = 6250 ohm So the correct ans is (c)= 6250 ohm

 Kuldeep Bisht said: (Oct 9, 2011) Primary resistence R'=R2/(K)2 here k=N2/N1=10/50=0.2 hence R'=250/0.2*0.2=6250 Ohm

 Amit Ranjan said: (Oct 11, 2011) Eqv.resistance referred to primary=r1+r2/(k*k) Here r1 is not given k=10/50=1/5 Hence ans = 250/(1/25) = 6250 ohm.

 Sunil Gorga said: (Nov 15, 2011) v1i1=v2i2 v1*v1/r1=v2*v2/r2 (v1/v2)^2=r1/r2 we know n1/n2=v1/v2 so (50/10)^2=r1/250 r1=250*5=6250

 Anil said: (Jan 23, 2012) Resistance matching R1=(n1/n2)^2*rL hence, r1=(50/10)^2*250 = 25*250 =6250 ohm

 Mahendra Chauhan said: (Mar 20, 2012) # given data primary coil turns=50,secondary coil turns=10 & secondary load 250 ohm. #equation N=secondary coil turns/primary coil turns (Rpri=reflected in to primary) Rpri=(1/n)^2*RL so N =10/50 =0.2 Rpri =(1/0.2)^2*250 =(5)^2*250 =25*250 =6250.

 Mahendra Dhakchavle said: (Apr 15, 2012) R2=250 k=n1/n2=50/10 R1=R2*k^2 =250*(2500/100) R1=6250ohm

 Kalyan said: (May 10, 2012) Rs=250 I1^2Rs=I2^2Rf (I1/I2)^2*Rs=Rf From Transformation ratio N2/N1=I1/I2=K (50/10)^2*250=Rf 25*250=Rf Rf=6250ohm

 Sunil Keshari said: (May 27, 2012) N1=50 N2=10 R2=250 ohm K=(N2/N1) (R2/R1)=K^2 (250/R1)=(10/50)^2 R1=(2500*250)/100 R1=6250 ohm

 Nidhi M J said: (Jun 10, 2012) Copper losses produced by r2 in primary side must be same as that in secondary side. I1^2*r2'=I2^2*r2 R2'= (I2/I1) ^2*r2 Where I2/I1=N1/N2.

 Virendra Ranpise said: (Aug 23, 2012) Resistance ratio=R2/R1 Xmer ratio(K)=N2/N1 Where, R1=Primary winding resistance R2=secondary winding resistance N1=Primari winding turns N2=secondary winding turns FORMULA FOR CALCULATING R1 R2/R1 = K square i.e. R2/R1 = (N2/N1)square 250/R1 = (10/50) square So R1 = (250) / ((10/50) square) R2=6250 ohm

 Akshat Gupta said: (Aug 31, 2012) Where n1=50 n2=10 r2=250ohm so resistance matching r1= (n1/n2)^*rl hence, r1=(50/10)^2*250 =25*250 =6250 ohm

 S.Anjineyulu Naik said: (Oct 1, 2012) Turn ratio, k=N2/N1. =10/50. =1/5=0.2. Actual resistance in secondary circuit is R2=250 ohm's. Reflective resistance means, the secondary resistance referred to primary winding is, R2'=R2/k^2. =250/ (0.2) ^2. =250/0.04. =6250 ohm's.

 Mallikarjun said: (May 24, 2013) R2' = r2/(kxk). r2 = 250 ohms. k = n2/n1 = 0.2. (kXk) = 0.04. R2' = 250/0.04 = 6250.

 Yatish Ahire said: (Jun 1, 2013) Primary resistance R1 = R2/(K)2. Here, K = N2/N1 = 10/50 = 0.2. Hence, R' = 250/0.2*0.2 = 6250 Ohm.

 Ododo said: (Jun 12, 2013) Please am confused, turns ratio is it the same as transformer ratio? I saw that turns ratio = N2/N1, and I still saw that turns ratio = N1/N2, which one is correct with proofs please.

 Engr. Mamoona Akbar said: (Jan 17, 2014) t2/t1 = sqrt (load impedance/source impedance). 10/50 = sqrt (250/x). 0.2*0.2 = 250/x. x = 250/0.04. x = 6250.

 Eshan Mishra said: (Feb 16, 2014) There is difference b/w the terms if simply turn ratio, voltage ratio is mention and transformation ratio is mention in the question. Eg:- transformation ratio is k, k=[V2/V1=N2/N1=I1/I2]. Simple turn ratio, voltage ratio is equal to 1/k N1/N2, V1/V2. And there is one more important relation, (V2/V1)=Square root(R2/R1).

 Arun Kumar Raju C said: (Apr 4, 2014) Ns/Np = sqrt(load resistance/source resistance).

 Akash.Bhure said: (Apr 29, 2014) Solution: No.of turns in the primary(N1) = 50. No.of turns in the secondary(N2) = 10. Turns ratio(K) = N2/N1 = 10/50 = 0.2. Secondary load resistance(R2) = 250 Ohm. Reflective resistance(R1) = R2/K^2. (R1) = 250/(0.2)^2. (R1) = 250/0.04 = 6250 ohm's.

 Sandip Chhatrola said: (Aug 31, 2014) K^2 = R2/R1. 1/25 = 250/R1. R1 = 6250 ohm.

 Bhawana Singh said: (Aug 19, 2015) Turn ratio will proportional to square of load then square of resistance in secondary upon primary 2n square.

 Rudra said: (Aug 24, 2015) What will be the Phasor diagram for it?

 Santosh Murkut said: (Mar 24, 2016) The transformation ratio is said that N2/N1 = V2/V1 = I1/I2 = K. Hence, 1) A resistance R1 in primary become K^2 * R1 when transferred to the secondary. 2) A resistance R2 in secondary become R2 / K^2 when transferred to the primary. Therefore, R1 = 250 / (10/50)^2 = 6250 ohm.

 Vyankatesh Badgujar said: (Nov 14, 2016) N1= 50 , N2 = 10. Turn ratio K = N2/N1 = 10/50, K = 1/5 = 0.2, Now, R2/R1 = K^2. R1 = R2/K^2, = 250/0.2^2, R1 = 6250 ohms.

 Sandeep Kumar said: (Jan 8, 2017) N2/N1= Sq.rt(R2/R1) 10/50 = Sq.Rt(250/R1) (1/5)^2 = 250/R1. R1=250*25 = 6250.

 Arjun said: (Jan 16, 2017) Reflective resistance = {(1/k^2)*Rload}.

 Rocky said: (Mar 1, 2017) Transformation ratio is N2/N1. Am I right?

 Faisal said: (Jun 17, 2017) The Formula is this, R1=(N1/N2)^2 RL. and R1 is given, N1 is given, N2 is given, So, 250=(50/10)^2 RL. 250 = 25 RL. Therefore, RL = 250 * 25 = 6250.

 Tom said: (Jul 31, 2017) Here, n2/n1=r1/r2.

 Paul said: (Aug 28, 2017) Ododo is the only one making sense here. k = turns ratio = N2/N1 (This is most often the conclusion based on the 20mins I've spent on the web researching this).

 Sumit said: (Sep 26, 2017) If primary side 1000 turn and 1000 watt on primary side find out secondary side pawer in watt if seconady turn 100.

 Tutun Mondal said: (Dec 27, 2017) K=N2/N1=1/5. SECONDARY TO PRIMARY R1=R2/K^2 =250/(1/5)^2=250*25=6250OHMS.

 Abhishek Mohapatra said: (Jan 7, 2018) From the basics: You have to find what resistance on primary will have similar effect as 250 on secondary. in ideal transformer power associated with primary equals secondary hence V2^2/250 = v1^2/Rreq. similarly V2*I2 =V1*I1. if you know what voltages are related in the same way as a number of turns i.e V2/V1 = N2/N1 then you can easily relate all currents and impedances.

 Vaibhav said: (Apr 8, 2018) Can I find reflected impedance or turns ratio if the only efficiency of the transformer is provided?

 Majid Mahmood said: (Aug 19, 2019) According to my calaculation: v1i1 = v2i2 v1*v1/r1 = v2*v2/r2 (v1/v2)^2 = r1/r2. We know n1/n2 = v1/v2 so (50/10)^2 = r1/250 => 25 = r1/250, r1 = 250 * 25 = 6250.

 Richa said: (Oct 30, 2020) Transformation ratio is N1 (Primary)/N2 (secondary).

 Suresh said: (Jul 27, 2021) Voltage of secondary 200v, transformer ration N1:N2= 200:100, X=12 Ohms and Rl = 4 Ohms. Estimate the RMS value of the primary current I1 and Secondary Current I2 and Estimate the power in watts.