Antennas Multiple Choice Questions & Answers on “Radiation – Basic Maxwell Equations”.
1. The Maxwell equation ∇×E=(frac{-partial B}{partial t}) is derived from which law?
a) Amperes law
b) Faradays Law
c) Lens law
d) Gauss law
Answer: b
Clarification: Faradays law states that emf generated around a loop of wire in magnetic field is proportional to the rate of change of time-varying magnetic field through the loop.
Amperes law gives ∇×H=J
Lens law gives only the reason for the negative sign in the Faradays law of induction.
Gauss’s law states that the net flux of an electricfield in a closed surface is directly proportional to the enclosed electric charge.
2. The minus sign in the Faradays law of induction is given by ______
a) Lens Law
b) Gauss law
c) Amperes Law
d) Gauss law
Answer: a
Clarification:Lens law gives only the reason for the negative sign in the Faradays law of induction
emf=(-frac{partial phi}{partial t})
The minus sign indicates the direction of induced current.
3. Which of the following Maxwell equation is obtained from Amperes law?
a) ∇×H=J
b) emf=(-frac{partial phi}{partial t})
c) ∇×E=(frac{-partial B}{partial t})
d) ∇×D=ρv
Answer: a
Clarification:
- Faradays Law : ∇×E=(-frac{partial B}{partial t})
- Amperes Law : ∇×H=J+(frac{partial D}{partial t})
- Gauss Law for electric field : D=ρv
- Gauss law for magnetic field : ∇.B=0
4. Gauss for the Magnetic Field is given by ______
a) ∇.B=0
b) ∇×B=ρv
c) ∇×B=0
d) ∇.B=ρv
Answer: a
Clarification: Gauss law for magnetic field states that the net flux out of any closed surface is zero.
∇.B=0
This Maxwell equation is one of the equation used to determine the boundary conditions.
5. Gauss for the Electric Field is given by ______
a) ∇.D=0
b) ∇×D=ρv
c) ∇×D=0
d) ∇.D=ρv
Answer: d
Clarification:Gauss’s law for electric field states that the net flux of an electricfield in a closed surface is directly proportional to the enclosed electric charge. ∇.D=ρv
This Maxwell equation is one of the equation used to determine the boundary conditions.
6. Which of the Following Maxwell equation is for nonexistence of isolated magnetic charge?
a) ∇×E=-(-frac{partial B}{partial t})
b) ∇×H=J
c) ∇.D=ρv
d) ∇.B=0
Answer: d
Clarification: Gauss law for magnetic field states that the net flux out of any closed surface is zero.
∇.B=0
This is satisfied only when two different poles of magnet exist. So this Maxwell equation proves for the nonexistence of the isolated magnetic charge.
- Faradays Law : ∇×E=(-frac{partial B}{partial t})
- Amperes Law : ∇×H=J
- Gauss Law for electric field : ∇.D=ρv