If the self-inductance of an iron ore inductor increases from 0.01 m H to 10mH on introducing the iron core into it, what is the relative permeability of the core used?

An iron-cored solenoid has self inductance 2.8 H. When the core is removed, the self inductance become 2mH. What is the relative permeability of the core used?

The core of toroid having 3,000 turns has inner and outer radii of 11 cm and 12 cm respectively. The magnetic field in the core for a current of 0.70 A is 2.5 T. What is the relative permeability of the core?

A Rowland ring has 10^3 turns per uit length. On passing a current of 2 A, magnetic induction is measured to be 1.5 Wb m^-2 . Calculate relative permeability of the core.

What is the purpose of using soft iron core in galvanometer.

The current in a self-inductance L = 40 mH is to be increased uniformly from 1 A to 11 A in 4 millisecond. The e.m.f. induced in the inductor during to process is

An air-cored solenoid is of length 0.3 m area of cross-section 1.2 xx 10^-3m^2 and has 2500 turns. Around tis central section, a coil of 350 turns is wound. The soelnoid and the coil are electrically insulated from each other. Calculate the e.m.f. induced in the coil , if the intial current of 3 A in the solenoid is reversed in 0.25 s.