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51.

Calculate the conduction density of a material with resistivity of 0.02 units and electric intensity of 12 units.(a) 300(b) 600(c) 50(d) 120I have been asked this question in my homework.This question is from Maxwell Law 2 topic in division Maxwell Equations of Electromagnetic Theory

Answer»

The correct option is (b) 600

The BEST EXPLANATION: The conduction density is GIVEN by Jc = σE, where σ is the inverse of resistivity and it is 1/0.02 = 50. Thus we get, Jc = 50 x 12 = 600 UNITS.
Discussion
52.

Find the conduction current density of a material with conductivity 200units and electric field 1.5 units.(a) 150(b) 30(c) 400/3(d) 300The question was posed to me in final exam.I'm obligated to ask this question of Maxwell Law 2 in chapter Maxwell Equations of Electromagnetic Theory

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Correct choice is (d) 300

To explain: The conduction current DENSITY is given by Jc = σE, where σ = 200 and E = 1.5. Thus we GET, Jc = 200 X 1.5 = 300 units.
Discussion
53.

Find the displacement current density of a material with flux density of 5sin t(a) 2.5cos t(b) 2.5sin t(c) 5cos t(d) 5sin tI had been asked this question at a job interview.My doubt stems from Maxwell Law 2 topic in portion Maxwell Equations of Electromagnetic Theory

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Right answer is (c) 5COS t

Easiest explanation: The displacement current DENSITY is the derivative of the flux density. Thus Jd = dD/dt. PUT D = 5sin t in the equation, we GET Jd = 5cos t units.
Discussion
54.

In dielectric medium, the Maxwell second equation becomes(a) Curl(H) = Jd(b) Curl(H) = Jc(c) Curl(E) = Jd(d) Curl(E) = JdI had been asked this question during an interview for a job.I'd like to ask this question from Maxwell Law 2 topic in portion Maxwell Equations of Electromagnetic Theory

Answer» RIGHT choice is (a) CURL(H) = Jd

Easiest EXPLANATION: In DIELECTRIC medium conductivity σ will be zero. So the current density has only the displacement current density. Thus the Maxwell equation will be Curl(H) = Jd.
Discussion
55.

The Maxwell second equation that is valid in any conductor is(a) Curl(H) = Jc(b) Curl(E) = Jc(c) Curl(E) = Jd(d) Curl(H) = JdThe question was asked in an online interview.My question is based upon Maxwell Law 2 topic in portion Maxwell Equations of Electromagnetic Theory

Answer»

Correct option is (a) CURL(H) = Jc

The explanation is: For conductors, the conductivity PARAMETER σ is significant and only the conduction current DENSITY EXISTS. Thus the COMPONENT J = Jc and Curl(H) = Jc.
Discussion
56.

Maxwell second equation is based on which law?(a) Ampere law(b) Faraday law(c) Lenz law(d) Coulomb lawThe question was posed to me in a national level competition.The above asked question is from Maxwell Law 2 in section Maxwell Equations of Electromagnetic Theory

Answer»

The correct option is (a) Ampere LAW

Best explanation: The second Maxwell equation is BASED on Ampere law. It states that the FIELD intensity of a SYSTEM is same as the current ENCLOSED by it, i.e, Curl(H) = J.
Discussion
57.

Calculate the emf of a material having flux density 5sin t in an area of 0.5 units.(a) 2.5 sin t(b) -2.5 cos t(c) -5 sin t(d) 5 cos tI have been asked this question in quiz.My question is based upon Maxwell Law 1 in division Maxwell Equations of Electromagnetic Theory

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Right choice is (d) 5 COS t

The explanation: The emf can be WRITTEN as Vemf = -d(∫B.ds)/dt. It can be written as Vemf = -B= -5sin t, since the integration and DIFFERENTIATION gets cancelled.
Discussion
58.

Calculate the emf of a material having a flux linkage of 2t^2 at time t = 1second.(a) 2(b) 4(c) 8(d) 16This question was addressed to me in a job interview.This intriguing question originated from Maxwell Law 1 topic in portion Maxwell Equations of Electromagnetic Theory

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Right ANSWER is (b) 4

The explanation: The emf of a MATERIAL is given by Vemf = -dλ/dt. On substituting λ = 2t^2, the emf is 4t. At t = 1 sec, the emf will be 4 units.
Discussion
59.

When the Maxwell equation is expressed in frequency domain, then which substitution is possible?(a) d/dt = w/j(b) d/dt = j/w(c) d/dt = jw(d) Expression in frequency domain is not possibleThe question was posed to me during a job interview.The question is from Maxwell Law 1 in division Maxwell Equations of Electromagnetic Theory

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Correct OPTION is (c) d/dt = JW

The explanation: The conversion of TIME to frequency domain in MAXWELL equation is given by the Fourier Transform. Differentiation in time gives jw in frequency domain. Thus d/dt = jw in frequency domain.
Discussion
60.

Find the electric field applied on a system with electrons having a velocity 5m/s subjected to a magnetic flux of 3.6 units.(a) 15(b) 18(c) 1.38(d) 0.72I had been asked this question in an online interview.I'm obligated to ask this question of Maxwell Law 1 topic in section Maxwell Equations of Electromagnetic Theory

Answer»

Correct choice is (b) 18

Easiest explanation: The electric field intensity is the PRODUCT of the velocity and the magnetic flux density. Thus E = v x B, on substituting v = 5 and B = 3.6, we GET E = 5 x 3.6 = 18 units.
Discussion
61.

Which of the following relations holds good?(a) Bq = ILE(b) E = ILBq(c) Eq = ILB(d) B = ILEqThe question was posed to me in quiz.This interesting question is from Maxwell Law 1 topic in division Maxwell Equations of Electromagnetic Theory

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Correct option is (c) EQ = ILB

Best explanation: The force of a electrostatic field in given by F = Eq. The force on a conductor is given by F = BIL. In the CASE when a charge EXISTS on a conductor, both the FORCES can be equated. Thus Eq = BIL is true.
Discussion
62.

Find the Maxwell first law value for the electric field intensity is given by A sin wt az(a) 0(b) 1(c) -1(d) AThe question was asked in final exam.My enquiry is from Maxwell Law 1 topic in division Maxwell Equations of Electromagnetic Theory

Answer» CORRECT choice is (a) 0

To explain I would say: The VALUE of Maxwell FIRST equation is Curl(E). The curl of E is zero. THUS for the given field, the value of Maxwell equation is zero. Thus the field is irrotational.
Discussion
63.

Which of the following identities is always zero for static fields?(a) Grad(Curl V)(b) Curl(Div V)(c) Div(Grad V)(d) Curl(Grad V)I have been asked this question in my homework.Asked question is from Maxwell Law 1 in portion Maxwell Equations of Electromagnetic Theory

Answer» CORRECT choice is (d) Curl(Grad V)

To explain: The curl of GRADIENT of a vector is always ZERO. This is because the gradient of V is E and the curl of E is zero for static fields.
Discussion
64.

The curl of the electric field intensity is(a) Conservative(b) Rotational(c) Divergent(d) StaticThe question was posed to me in quiz.The question is from Maxwell Law 1 topic in section Maxwell Equations of Electromagnetic Theory

Answer»

The correct choice is (B) Rotational

The best I can explain: The curl of electric field intensity is Curl(E). From MAXWELL law, the curl of E is a non-zero VALUE. THUS E will be rotational.
Discussion
65.

The correct sequence to find H, when D is given is(a) D-E-B-H(b) D-B-E-H(c) It cannot be computed from the data given(d) D-HI got this question in an international level competition.My question is based upon Maxwell Law 1 in portion Maxwell Equations of Electromagnetic Theory

Answer»

Correct answer is (a) D-E-B-H

To EXPLAIN: There is no direct RELATION between D and H, so the option D-H is not possible. USING the formula D = εE, the parameter E can be computed from D. By Maxwell equation, Curl(E) = -dB/dt, the parameter B can be calculated. Using the formula B = μH, the parameter H can be calculated. THUS the sequence is D-E-B-H.
Discussion
66.

The benefit of Maxwell equation is that(a) Any parameter can be calculated(b) Antenna can be designed(c) Polarisation of the wave can be calculated(d) Transmission line constants can be foundThe question was posed to me during an interview.My question is from Maxwell Law 1 topic in chapter Maxwell Equations of Electromagnetic Theory

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Correct choice is (a) Any parameter can be calculated

For explanation: The MAXWELL EQUATION relates the parameters E, D, H, B. When one parameter is known the other parameters can be easily calculated. In other words, it is used to relate an electric field parameter with its EQUIVALENT magnetic field.
Discussion
67.

The first Maxwell law is based on which law?(a) Ampere law(b) Faraday law(c) Lenz law(d) Faraday and Lenz lawThe question was posed to me in an online interview.This interesting question is from Maxwell Law 1 in section Maxwell Equations of Electromagnetic Theory

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Right OPTION is (d) Faraday and Lenz law

For EXPLANATION I would say: The first Maxwell equation states that CURL(E) = -dB/dt. It is BASED on the emf concept. Thus it is derived from the Faraday and Lenz law.
Discussion