Question

True/False please

1. The magnetic field is always conservative

2. Gauss'law for magnetism reflects the fact that there are no electric monopoles.

3. An electrically charged rod will attract a piece of magnetic material.

4. In an AC circuit, the complex power S represents the power supplied to the capacitors and inductors.

5. The capacitance of a parallel plate capacitor increases when a piece of dielectric material is inserted between the plates.

6. If an AC circuit has tow sources with different frequencies, we can add the solutions for each source in phasor space.

7. The ultimate source of all electromagnetic phenomena is electric charges in motion.

8. In an AC circuit, the average power supplied to a resistor is zero.

9. The magnetic field cannot ever do any work.

10. The instantaneous power supplied to any circuit element is always p(t) = i(t)v(t)

11. Both the voltage and current for an inductor must be continuous in time.

12. The relative permeability of a ferromagnetic substance is <1

Thank you!

Answer 1

1) Magnetic field is neither conservative nor non conservative. This statement is false.

2) Gauss law in magnetism states that divergence of magnetic field is zero which is equivalent to the statement that magnetic monoploes do not exist because if divergence of magnetic field is zero than magnetic field lines are closed curves. Hence this statement is true.

3) Piece of magnetic material can be attracted by another magnetic material only. Therefore charged rod will not attract it. This statement is False.

4) Complex power in AC circuits is sum of Active power and Reactive power. Therefore this statement is false.

5) As on introduction of dielectric between the plates the potential difference across the plates decreases but charge on each plates remains same, hence its capacity increases. Therefore this statement is true.

6) In phasor we deal with only one frequency therefore this statement is false.

7) Source of electric phenomenon is charge, it creates magnetic effect, when is in motion, and emits electromagnetic radiation when accelarating, therefore statement is incomplete hence this is false.

8) In an AC circuit AC power supplied to inductor and capacitor is zero as both can act as active as well as passive ie they store energy and supply it back to the circuit when needed. Hence power consumed by them is equal to the power delivered by them and average power is zero. But resistance is only passice circuit element, it only can consume energy therefore average power for resistance could not be zero. This statement is false.

9) As magnetic force acting on charge particle is always perpendicular to the velocity or displacement of the particle. Therefore magnetic force can't do any work on charge particle and it's kinetic energy remains constant. This statement is true.

10) Instantaneous power supplied in AC circuit is

P = VI Cos ©, where Cos © is power factor. Hence this statement is false.

11) This statement is true.

12) As magnetic susceptibility of ferromagnetic substance is very very larger than 1 hence rekative permeability is also very very greater than 1.Thereforw this statement is false.