Practice Questions
- Explain B-H curve of a magnetic material.
- Explain the following terms: (1) Fringing and leakage (ii) Magnetic circuit .
- Why do eddy current losses occur in a magnetic material? How can they be reduced?
- What do you mean by transformer on no-load and load conditions? Explain with phasor diagram.
- Draw the phasor diagram of transformer at lagging power factor and explain it.
- Derive E.M.F. equation of a D.C. machine.
- Explain the working principle of 3-phase induction motor.
- Write short notes on synchronous machine.
- A 6-pole lap wound armature has 840 conductors and flux per pole of 0.018 Wb. Calculate the emf generated when the machine is running at 600 rpm.
- Explain open circuit and short circuit tests on single phase transformer.
- A mild steel ring having a cross sectional area of 5 cm² and a mean circumference of 40 cm h a coil of 200 turns bound uniformly around it. Calculate: (1) The reluctance of the ring (ii) The current required to produce a flux of 800 μWb in the ring. Assume relative permeability of mild steel to be 330 at the flux density developed at the cone.
- A 25 KVA 2200/220V, 50 Hz single phase transformer has the following resistance and leakage reactance- R₁ = 0.892, R₂ 0.00902 X₁ = 3.292, X₂ = 0.0302 . Calculate (1)Equivalent resistance referred to primary side.(2) Equivalent reactance referred to primary side.(3) Equivalent resistance referred to secondary side.
- Define the following: (i) Active power (ii) RMS value in single phase a.c. circuit (iii) Reactive power
- A balanced star connected load is supplied a symmetrical 3-phase, 410 V system. The current in each phase is 30A and lags 30° behind the phase voltage, find: (1) Phase voltage (ii) Active power (iii) Reactive power drawn by the load .
- A resistance of 2402, a capacitor of 15 µF and an inductor of 0.16 H are connected in series with each other. A supply of 240V, 50 Hz is applied to the ends. Calculate : The current in the circuit (ii) The potential difference across each element (iii) The frequency to which the supply would need to be changed so that the current would be at unity power factor and find the current at this frequency.
- What is power factor? Discuss the practical importance of power factor.
- Explain working principle of 3 phase induction motor.
- Draw and explain torque speed characteristic of 3 phase induction motor.
- Explain construction details of synchronous motor.
- How self excited DC generators are classified and draw their symbol.
- With the help of circuit diagram, truth table explain the working of J-K flip-flop. Explain race around condition in J-K flip-flop.
- Design half adder using only NAND gate.
- Draw and explain V-I characteristic of diode.
- Draw circuit and characteristics of CE transistor configuration.
- Explain biasing of transistor.
- Explain transistor current components for typical PNP transistor.
- A resistance of 20 ohm and inductance of 0.2 H and capacitance of 100 µF are connected in series across 220V, 50 Hz mains. Determine the Impedance and current ?
- In the circuit shown below the node voltage VA is ___V
* Questions will be updated . Check regularly .
* Repeated questions are the most important .
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