JNTU
JNTU B.Tech II ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (March/April - 2021 - R15/R13)
Answer any Five Questions. All Questions Carry Equal Marks.
Main
In the circuit shown in figure 1, determine Vx.
Answer
To determine Vx using Nodal Analysis, identify the node voltage Vx at the junction where the current source and resistors meet. Applying Kirchhoff's Current Law (KCL) at this node:
Assuming standard circuit parameters where Vsource is the input voltage and R1, R2 are the connected resistances, isolate Vx by grouping terms: Vx(1/R1 + 1/R2) = Isource + Vsource/R1. Solving for Vx yields the final node voltage value in Volts.
For the circuit shown in figure 2, calculate Io.
Answer
To calculate Io, apply Mesh Analysis or Thevenin's Theorem. Using Mesh Analysis, define loop currents I1 and I2. Apply Kirchhoff's Voltage Law (KVL) to each loop:
For the loop containing Io, write the KVL equation incorporating all resistors and voltage sources. Solve the resulting system of linear equations for the mesh current passing through the branch of interest. If Io is defined as a branch current shared by two meshes, Io = I1 - I2 (or vice versa depending on direction). The resulting value provides the current in Amperes.
Explain the construction and working of PMMC instrument with the help of a neat sketch.
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Explain the operation of three point starter with the help of neat diagram.
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Calculate the flux in a 4-pole dynamo with 722 armature conductors generating 500V when running at 1000rpm. When the armature is (i) Lap wound (ii) wave wound.
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What are different types of DC motors? Explain the significance of back emf in self-excited motors.
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Explain the power stages in the DC generator.
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A 200kVA transformer has an efficiency of 98% at full-load. If the maximum efficiency occurs at three quarters of full load, calculate: (i) iron losses at full load (ii) Cu losses at full load (iii) efficiency at half-load. Ignore magnetizing current and assume a pf of 0.8 at all loads.
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Explain how RMF is produced in a three phase induction motor?
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A 4 pole 3 phase, 50Hz, star connected alternator has 60 slots, with 4 conductors per slot. Coils are short pitched by 3 slots. If the phase spread is 60°, find the line voltage induced for a flux per pole of 0.943 Wb distributed sinusoidally in space. All the turns per phase are in series.
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Explain how flux is maintained constant in the transformer core irrespective of the load connected to it.
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Explain, with a diagram, how full-wave rectification is obtained using a bridge rectifier circuit.
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Draw and explain VI characteristics of PN diode.
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Draw the block diagram of CRO and explain the function of each block.
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Derive the expression for the electro-static deflection sensitivity of a cathode ray tube.
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