537 questions and answers
A two element series circuit consumes 700 V of power and has power factor of 0.707 leading when energized by a voltage source of waveform \(v=141\sin\left(314t+30^{\circ}\right)\). Find out the circuit element.
The power dissipated by the coil is \(P_C=I_{rms}V_{rms}\ cos\ \phi\) For this problem \(V_{rms}=\frac{V_{peak}}{\sqrt2}=\frac{141}{\sqrt2}=100\ V\)
The galvanometer shown in the circuit has a resistance of 5 Ω. Find the current through the galvanometer using Thevenin’s theorem.
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Fig.22(a)
Equivalent resistance of the circuit \(R_{th}=\frac{10\times15}{10+15}+\frac{12\times16}{12+16}=6+6.86=12.86\ \mathrm{\Omega}\)
Derive a mathematical expression for the average real power deliver by a single phase a.c. source with an e.m.f of \(e=\sqrt{2}E_m\sin\omega t\) when the source current is \(i=\sqrt{2}I_m\sin\left(\omega t-\theta\right)\). Define power factor of an a.c. circuit. State the major disadvantage of poor power factor.
\(e=\sqrt2E_m\sin{\omega t}\) … (1) \(i=\sqrt2I_m\sin{(\omega t-\theta)}\) …(2)
Derive an expression for the resonant frequency of a parallel circuit, one branch consisting of a coil of inductance L and resistance R and the other branch of capacitance C.
The series RL circuit with parallel C is given in Fig. 19. The designed circuit consists of resistance R, inductance L are in series with parallel configuration of capacitance C. Let us consider the current I flowing through the RLC circuit by the a.c. voltage source with constant value of V.
Explain
In this transformation any resistance in delta network can be found out if the resistances of corresponding star network are known. Here the branch resistances in the star connections are
A circuit receives 50 A current at a power factor of 0.8 lag from a 250, 50 Hz, 1-ph A.C. supply. Calculate the capacitance of the capacitor which is required to be connected across the circuit to make the power factor unity.
From the given data, we have \(cos\ \theta=0.8\), Or \(\theta=\cos^{-1}{0.8}={36.86}^0\)
Find the current in each branch of the network using Kirchhoff’s law
Fig.23
Applying KVL in mesh I, II and II respectively \(-2I_1-3I_2+{7I}_3=12\) … (1)
Define the terms accuracy, Precision, Resolution, Drift and Relative limiting error.
Accuracy of measurements mean conformity to truth. It is the closeness with which an instrument reading approaches the truth value of the quantity being measured
Explain the difference between Dynamometer type wattmeter and induction type wattmeter.
i. Working torque comparatively weaker. i. Working torque comparatively stronger.
Define gauge factor of a strain gauge & obtain its expression.
It is defined as the ratio of per unit change in resistance to per unit change in length. Expression: Gauge factor \(\left(G_f\right)=\frac{\Delta R/R}{\Delta L/L}\)
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