SRM University 2007 B.Tech Electronics and Communications Engineering BANK : CUIRCUIT THEORY_UNIT – IV - Question Paper

15. Two impedance Z1 and Z2 are connected in series with the primary and secondary winding of an ideal transformer were the primary coil has j2 ? and secondary coil has j3 ? reactance. obtain the mutual reactance and inductance if w=100 rad / sec and K=1.

16. Two coupled coils have K=0.8 N1=500 turns N2=1000 turns and mutual flux being 0.9wb, obtain the primary coil flux if the primary current 10A.

17. Write down the mesh formula for the loops A B C D and P Q R S in the coupled the circuit shown in the fig.








18. Find the conductively coupled equivalent circuit shown in the fig.








19. Write down the mesh formula for the network shown in the fig.










20. Two coupled coils of self inductance L1 = 50mH, L2 = 70mH, K = 0.65 (in the air) obtain the voltage in 2nd coil (Primary current = five sin 314 t A and N2=500 turns.

21. In the coupled circuit shown in the fig. obtain the input impedance and net inductance. Where K = 0.5, L one = L2 = 1H.









22. Find the equivalent circuit and the net inductance of the series connected coupled
circuit shown in the fig. where K12 = 0.6, K23 = 0.5 and K13 = 0.4

23. What are the values of self and mutual inductance for the 2 coupled coils one & two if K=1 and N1=500 turns N2=750 turns I1(primary current)=5A ?1 = 50mwb and ?2 = 60mwb.

24. Two coupled coils are K = 0.6 N1=250 turns N2 = 500 turns and mutual flux being 0.7wb. obtain the primary coil flux if the primary current 10A.

25. Two coils of self inductance L1=2H, L2=4H are coupled in such way that M=1.5H assuming the mutual inductance to +ve as per the dot convention , obtain the amount of energy stored after 0.2 sec for the circuit connected to a DC source of 12V.

26. Write the Mesh equations for the transformer circuit shown in the figure









27. Show that for an ideal transformer L1L2 - M2=0






28. For the beneath figure represents a coupled coil circuit where L1=20mH and L2=50mH. If the coefficient of mutual induction is 0.8, obtain the value of mutual inductance and write down the mesh formula in time domain.










29. Find V2 in the circuit shown in the figure such that current in the left hand loop (loop 1) is Zero. presume V1= five phase 0°









30. In the circuit shown in the figure shown in the figure , write the loop formula in time domain if L1 = L2 = 1H, v1= 10 sin wt , v2 = five sin (wt + 30°). presume M= 10H










PART B

1. Two coupled coils with respective self inductance L1 = 0.8H and L2 = 0.2 H have a coupling coefficient of 0.6. Coil two has 500 turns. If the current in coil one is i1(t)= 10 sin200t . Determine the voltage at coil two and maximum flux set up by coil one

2. In a series fed double tuned circuit a maximum voltage gain of 20 was found at a resonance frequency is two µF. The maximum output voltage at resonance is 50 V. compute.
(i) Supply Voltage
(ii) Primary and Secondary self inductances
(iii) the critical co- efficient of coupling
(iv) The capacitance in the secondary circuit.
Assume that the primary and secondary resistance are of one ? and four ? resp.

3. The total inductance of 2 coils , A and B when connected in series is 0.5 H or 0.2 H depending on the relative direction of the current in the coils. Coil A when isolated from coil B, has a self inductance of 0.2 H. compute ( a) Mutual inductance ranging from the 2 coils (b) the self inductance of the coil B (c) the coupling factor ranging from the coils (d) the 2 possible values of the induced e.m.f. in coil A the current is decreasing at 1000A per 2nd in the series circuit.

4. Two coupled coils have L1 = 1H, L2=2H, M=1.2H. Assuming the inductance coils to be ideal. obtain the amount of energy stored after 0.1sec. of the circuit connected to a DC source 10V.

5. Find the conductively coupled equivalent circuit for the network shown in the fig.










6. Find the drop across RL for the circuit shown in figure.










7. Find the voltage drop across the capacitor and the resistor for the circuit shown in the figure.









8. Find the voltage drop across the resistance ‘r’ in the network shown in the figure.









9. Find the voltage V1 and V2 in the circuit shown in the figure.










10. Find an expression for the input impedance of the circuit shown in the figure.

Earning:   Approval pending.