Dear Deepak Pathak,

Main idea of generating AC magnetic field is to pass AC current.

Whatever be the shape and Topology of the solenoid coil , if you use an AC current/ voltage source of the desired frequency ( here upto 100 Hz ) , you will get AC magnetic field of that frequency ( after the transition time ) . The value ( 24 mT ) of magnetic field depends on the AC current , No of Turns and the permeability of the core material.

So, to calculate the value of the magnetic field you have to know the resistance and inductance of the solenoid and then you have to select AC power supply accordingly.

If you have any more query , please tell me and I will try to discuss to the best of my capacity.

For the measurement of AC magnetic field, you can use AC gauss meter or just a coil and AC voltmeter after having a calibration .

Thanks and Regards

N Das

Generally, take Nityananda Das' answer as the guideline for making the coil. In my opinion, do not try to calculate the equipment very accurately, as the reality may differ from the calculations. From my experience, I can tell you the performance of the coil that is in our lab: the solenoid is about 50 mm in diameter, winding made from 1.5 mm in diameter (which makes about 660 turns per metre), 13 layers of winding. Altogether: 8580 turns/metre. Air coil - no core inside. The current of 1 A generates about 7000 A/m of magnetic field in the midway point between coil's ends.

In your case, 24 mT of field induction is the equivalent of 19.2 kA/m, which is nearly threefold of what is generated in my coil.

It is not only the coil that is important: you must have the current source (not the voltage source) with sufficient capacity at 100 Hz. This frequency should be easily handled by acoustic amplifiers, but mind the voltage and current limits. Generally, the larger the coil, the larger inductive load, and voltage necessary to push the desired current through the coil may be surprisingly high. My "acoustic" (17 kHz) power supply, 400 W of capacity, is not sufficient to feed the coil at 100 Hz. The proper selection and matching with the coil of the power supply may be quite puzzling.