The core of an electromagnet should be a) soft iron.

Explanation: Soft iron is used as the core of an electromagnet because of its high magnetic permeability, meaning it can easily magnetize and demagnetize in response to an external magnetic field. When an electric current is passed through a coil wrapped around the soft iron core, it becomes strongly magnetized and creates a strong magnetic field. When the current is removed, the magnetism of the soft iron core quickly disappears, allowing the electromagnet to be turned on and off easily. Hard iron, on the other hand, retains its magnetism longer and is not suitable for electromagnets that need to be switched on and off frequently. Rusted iron is not ideal because the rust would interfere with the magnetic properties and reduce the efficiency of the electromagnet.

A) Soft iron should be the core of an electromagnet.

Soft iron is a ferromagnetic material that can be easily magnetized and demagnetized. When a current flows through the wire coiled around the soft iron core, it creates a magnetic field. The soft iron core intensifies the magnetic field by concentrating the magnetic flux lines within it. This results in a stronger magnetic force than the wire alone could produce. Therefore, soft iron is the ideal core material for electromagnets.

Hard iron, on the other hand, is a type of ferromagnetic material that is difficult to magnetize and demagnetize. Rusted iron is not suitable for a core material as it is corroded and not a good conductor of electricity. Hence, the correct answer is (a) soft iron.

Gauss’s law is more useful in the cases where the charge distributions:are made of discrete point charges (b) are finite in their special extent (c) symmetrical charge distribution (d) gives rise to inverse square law distributionIf 0.5 T filled over an area of 2 m2 which lies at an angle of 60o with the field. Then the resultant flux will be: (a) 0.25 T (b) 0.25 Wb (c) 0.5 T (d) 0.5 WbMagnetic induction at a point due to the current carrying conductor is determined by: Ampere’s law (b) Faraday’s law (c) Lenz’s Law (d) Newton’s lawOne Tesla is also equal to (a) Wb m-2 (b) Wb m2 (c) Wb m (d) NoneForce on a moving charge in a uniform magnetic field will be maximum, when angle between v and B is: (a) 00 (b) 300 (c) 600 (d) 900It is possible to set a charge at rest into motion with magnetic field Yes (b) No (c) Some Time (d) NoneAccording to Faraday’s law of electromagnetic induction, the induced emf is directly proportional to: (a) Magnetic Flux (b) Induced Current (c) Resistance of coil (d) Rate of change of magnetic fluxIf fingers of right hand show the direction of magnetic field and palm shows the direction of force, then thumb points for: (a) Torque (b) Voltage (c) Current (d) Induced emfThe induced current is a circuit can be increased by: (a) Using strong magnetic field (b) Moving loop faster (c) Replacing the loop by the coil of many turns (d) All a, b & c Mathematical form of ohm’s law is (a) I = VR (b) I = V/R (c) I = R/V (d) R = IV