List of top Geophysics Questions on Electromagnetic Theory and Electronics

Two long coaxial metal cylinders of inner radius \(r_1\) and outer radius \(r_2\) are separated by material of conductivity \(k\). If cylinders are kept at a potential difference of \(V\), the current flows from one to the other in length \(l\) is:

Match List I with List II:

LIST I	LIST II
A. Maxwell's First Equation	I. Modified Ampere's Law
B. Maxwell's Second Equation	II. Faraday's Laws of Electromagnetic Induction
C. Maxwell's Third Equation	III. Gauss Law in Electrostatics
D. Maxwell's Fourth Equation	IV. Gauss Law in Magnetostatics

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Which statements are correct for a P–N junction diode?
(A) For forward bias, P-side is connected to the positive terminal and N-side to the negative terminal of the battery.
(B) For forward bias, P-side is connected to the negative terminal and N-side to the positive terminal.
(C) For reverse bias, P-side is connected to the negative terminal and N-side to the positive terminal.
(D) For reverse bias, P-side is connected to the positive terminal and N-side to the negative terminal.
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In an LCR circuit, the current and emf differ in phase by $\Phi$. The value of $\Phi$ is:

In the case of a rolling solid sphere on an inclined plane making an angle of $30^\circ$ with the horizontal plane, the acceleration of the sphere rolling down the plane is (where acceleration due to gravity is $9.8 \, \text{m/s}^2$):

Consider a silicon p-n junction at $T = 300 \, \text{K}$ with doping concentrations of acceptor $N_A = 10^{16} \, \text{cm}^{-3}$ and donor $N_D = 10^{15} \, \text{cm}^{-3}$. Assume that intrinsic concentration $n_i = 1.5 \times 10^{10} \, \text{cm}^{-3}$, relative permittivity $= 11.7$, and $V_{bi} = 0.635 \, \text{V}$. The width of the space charge region in the p-n junction is:

	LIST I		LIST II
A.	Bipolar npn transistor operate in the cut-off mode.		I. The base-emitter is reverse biased and
B.	Bipolar npn transistor operate in the saturation mode.		II. Both the base-emitter and base
C.	Bipolar npn transistor operate in the inverse active mode.		III. The base-emitter is forward biased
D.	Bipolar npn transistor operate in the forward active mode.		IV. Both the base-emitter and bas

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	LIST I		LIST II
A.	∇ ⋅ E = ρ/ε₀		I. Gauss's Law in magnetostatics
B.	∇ ⋅ B = 0		II. Faraday's Law of electromagnetic Induction
C.	∇ × E = - ∂B/∂t		III. Gauss's Law in electrostatics
D.	∇ × B = μ₀J + μ₀ε₀ ∂E/∂t		IV. Modified Ampere's Law

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Which of the following statements are true for ideal PN junction current voltage relationship?
(A) The abrupt depletion layer approximation applies.
(B) The Maxwell-Boltzmann approximation applies to carrier statistics.
(C) The concept of low injection applies.
(D) The total current is not constant throughout the entire pn structure.
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Displacement current is not a conventional current but it is:

	LIST I		LIST II
A.	Intrinsic semiconductor		I. Used as a rectifier circuit
B.	N-Type Semiconductor		II. Pure form of Semiconductor
C.	P-Type Semiconductor		III. Doping of pentavalent impurity in semiconductor
D.	P-N Junction diode		IV. Doping of trivalent impurity in semiconductor

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Find the amplitude of the electric field in a parallel beam of light of intensity $2.0 \, \text{W/m}^2$: