Question

1. The average energy dissipated in an ideal (ideal means no resistance) inductor is
   1. zero.
   2. proportional to the inductance.
   3. proportional to both the inductance and frequency.
   4. proportional to the frequency.
   5. none of the above

2. The maximum power output in a series LRC circuit occurs when  
   1. X_L is greater than X_C.
   2. X_C is greater than X_L.
   3. (X_L - X_C)² is greater than R².
   4. (X_L - X_C)² is equal to R².
   5. X_C equals X_L.

3. True or False. Just as a changing magnetic field produces an electric field, a changing electric field produces a magnetic field.

4. True or False. The electric energy density in an electromagnetic wave is higher than its magnetic energy density.

5. If the magnetic field in an EM wave is in the x-direction and the electric field in the wave is in the y-direction, the wave is traveling in the
   1. x-y plane.
   2. direction halfway between the x- and y-directions.
   3. z-direction.
   4. x-direction.
   5. negative z-direction.

6. The energy per unit volume in an EM wave is
   1. equally divided between the electric and magnetic fields.
   2. almost entirely in the electric field.
   3. indeterminate.  
   4. almost entirely in the magnetic field.
   5. zero.

7. Two objects are in all respects identical except for the fact that one was coated with a substance that is an excellent reflector of light while the other was coated with a substance that is a perfect absorber of light. You place both objects at the same distance from a powerful light source so they both receive the same amount of energy, U, from the light. The pressure these objects will receive is such that:
   1. The reflecting objects receives a larger amount of pressure.
   2. Both objects receive the same amount of pressure.
   3. The reflecting object receives a smaller amount of pressure
   4. None of the above answers is correct.

please help!!

Answer 1

1) power factor of purely inductor circuit is equal to zero. Since in purely inductive circuit current and voltage difference by 90 degree. Pavg.=V×I×Cos(90)=0.

Hence average power dissipated will be equal to zero.

Clearly option (a) is correct.

2) power output in LCR circuit will be maximum if circuit is at resonance which means XL equal to XC.

Clearly option (d) is correct.

3) time varying magnetic field can create an electric field in similar manner an electric field also create magnetic field. When electric flux is changing then a virtual current is induced which is called displacement current this current causes magnetic field.

Hence the given statement is TRUE.

4)for an electromagnetic wave, the energy associated with the electric field is equal to the energy associated with the magnetic field.

Clearly this statement is a false statement.

5) the direction of propagation of electromagnetic wave is given by (E×B) vector.

It is clear that direction of propagation is perpendicular to both electric field vector and magnetic field vector. Hence option (C) is correct.