Which of the following is/are correct? 1.  Displacement current can exist in vacuum 2.  Magnetic field can exist without electric field 3.  Changing electric field necessarily produces magnetic field 4.  Displacement current is not a real current because it involves no charge transport

Solution

• Displacement current can exist in vacuum:
  True. Displacement current was introduced by Maxwell to correct Ampere’s law in cases where there is a changing electric field but no conduction current, like in a capacitor or even in free space (vacuum). Hence, displacement current can exist in a vacuum.
• Magnetic field can exist without electric field:
  True. A static magnetic field (like the field around a bar magnet) can exist without any associated electric field. Electric and magnetic fields are linked when changing with time, but a static magnetic field can independently exist.
• Changing electric field necessarily produces magnetic field:
  True. According to Maxwell’s equations, a time-varying electric field produces a magnetic field. This is the principle behind electromagnetic wave generation.
• Displacement current is not a real current because it involves no charge transport:
  True. Displacement current does not involve actual movement of charges; it is a mathematical term representing the effect of a changing electric field, not a flow of charges like conduction current.