List of practice Questions

Indicate a correct choice on currents during open circuit (OC) and short circuit (SC) tests of transformer
A 11kV/3.3kV, 100 MVA, 3-phase transformer has equivalent impedance seen from LV side of (1.2 + j4.8) Ω. The per unit impedance of the transformer is
If R and X are equivalent resistance and equivalent reactance of a transformer respectively, then at maximum voltage regulation, the power factor is
Two identical coaxial circular coils carry the same current 1 amp but in opposite directions. The magnitude of the magnetic field \( B \) at a point on the axis midway between the coils is
Magnetic dipole moment is ______ of the loop, its direction is normal to the loop
\( \nabla \cdot \vec{B} = 0 \), shows that
The reciprocal of reluctance is
The magnetization \( M \), in amperes per meter is
The slip-speed of a 3-\(\phi\), cage, 50 Hz, induction motor is 20 rpm at no-load. If slip-speed is doubled due to load, then the electrical equivalent of mechanical load will
Choose the correct statement of Reciprocity theorem in single source network:
If BW is bandwidth, \( \omega_r \) is resonant frequency and Q is quality factor of a resonant circuit, then Selectivity is defined as:
The response of a 1-$\phi$ R-L series circuit is \( i(t) = Ae^{-\frac{R}{L}t} + I_m \sin(\omega t - \theta) \). Then the supply voltage should be:
Point charges \( Q_1 = 1\text{nC} \) and \( Q_2 = 2\text{nC} \) are at a distance apart. Which of the following statement is \textbf{incorrect?
If \( \vec{D} = \epsilon \vec{E} \) and \( \vec{V} = \sigma \vec{E} \) in a given material, the material is said to be:
A source voltage of 100 V dc is applied across a RLC series circuit. Under steady-state conditions, voltages across each element is
The equivalent inductance of two equal inductances when connected in series aiding is 14 H and when connected in series opposing is 6 H. What is the coefficient of coupling?
Certain resistors connected in parallel and the equivalent resistance is \( X \). If one of the resistances is removed the equivalent resistance is \( Y \). What is the conductance value of removed resistance?
A signal of \( v = 5 + 10 \sin \omega t \) is applied across a \( 2\, \Omega \) resistor. The power dissipated in the resistor is
Three impedances \( 6 + j(10/3)\, \Omega \) each are connected in delta. The per-phase impedance of equivalent star circuit will be
The integrating factor of \[ \frac{dy}{dx} + y \cot x = 2x + x^2 \cot x \] is
Particular integral of \[ \frac{dy}{dx} + y = e^{x} \] is
If \[ f(x) = \begin{cases} -\pi, & -\pi<x<0 \\ x, & 0<x<\pi \end{cases} \] then the constant term of the Fourier series is
The mean and variance of a random variable \( X \) having a Binomial distribution are 4 and 2 respectively, then \( P(X=1) \) is
A 1-$\phi$, RC series circuit has \( R = 5\, \Omega \) and \( C = 10\, \mu F \). If the angular frequency of current is 20000 rad/sec, then the applied voltage
If the function \( u = \sin^{-1} \left( \frac{x^3 + y^3}{x + y} \right) \), then \[ x \frac{\partial u}{\partial x} + y \frac{\partial u}{\partial y} \] is