Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech II ELECTRICAL AND ELECTRONICS ENGINEERING Previous Question Paper (November/December - 2020 - R13)
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Main
For the bridge network shown in figure 1 determine the currents in each of the resistors.
Answer
To determine the currents in each resistor of a bridge network, apply Kirchhoff's Laws. First, define the nodes and assign loop currents (mesh analysis) or node voltages (nodal analysis). If using mesh analysis, write Kirchhoff's Voltage Law (KVL) equations for each independent loop:
For a bridge with resistors R1, R2, R3, R4 and a central bridge resistor R5, the system of linear equations is solved to find the mesh currents. The current through any specific resistor is then the algebraic sum of the mesh currents passing through it. If the bridge is balanced, the potential difference across the central resistor is zero, and the current through it is zero.
Differentiate between moving coil and moving iron instruments.
Answer
The differences between moving coil (Permanent Magnet Moving Coil - PMMC) and moving iron (MI) instruments are as follows:
- Operating Principle: PMMC operates on the principle of a current-carrying coil placed in a permanent magnetic field. MI instruments operate on the principle of attraction or repulsion of a soft iron piece in a magnetic field produced by a stationary coil.
- Current Type: PMMC is suitable only for DC measurements. MI instruments can measure both AC and DC quantities.
- Scale: PMMC instruments have a uniform (linear) scale. MI instruments have a non-uniform (cramped at the beginning) scale.
- Damping: PMMC uses eddy current damping, which is very effective. MI instruments typically use air-friction damping.
- Cost and Robustness: PMMC instruments are more expensive and delicate. MI instruments are cheaper, more robust, and can withstand higher overloads.
- Power Consumption: PMMC instruments generally have lower power consumption compared to MI instruments.
Classify Indicating type instruments. Give the applications of moving iron and moving coil instruments.
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Determine the current supplied by each battery in the circuit shown in Figure 2 using Kirchoff’s Laws.
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A 250-V, 4-pole, wave-wound d.c. series motor has 782 conductors on its armature. It has armature and series field resistance of 0.75 ohm. The motor takes a current of 40 A. Estimate its speed and gross torque developed if it has a flux per pole of 25 mWb.
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Classify DC Generators and explain about each of them.
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Explain the process of building up of voltage in a dc shunt generator. What is its significance?
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A 4-pole series motor has 944 wave-connected armature conductors. At a certain load, the flux per pole is 34.6 mWb and the total mechanical torque developed is 209 N-m. Calculate the line current taken by the motor and the speed at which it will run with an applied voltage of 500 V. Total motor resistance is 3 ohm.
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A 20kVA, single-phase transformer has 200 turns on the primary and 40 turns on the secondary. The primary is connected to 1000V, 50 Hz supply. Determine: i) The secondary voltage on open circuit; ii) The currents flowing through the two windings on full load; and iii) The maximum value of flux.
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Explain Synchronous impedance method to predetermine the voltage regulation of an alternator.
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State and prove the condition for maximum efficiency in a transformer.
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Explain how rotating magnetic field is produced.
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Explain about PNP and NPN Junction transistor. Discuss their characteristics and applications.
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Write short notes on SCR characteristics and applications.
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What is the difference between a CRT and CRO? Draw a neat block diagram of a general purpose CRO and explain functions of each block.
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