Question

In Electromagnetic methods of prospecting, which one of the given options is CORRECT about frequency and type of current source for the Primary field used?

• A. High frequency A.C.
• B. Low frequency A.C.
• C. Both high frequency A.C. and D.C.
• D. Low frequency D.C.

Hint:

In electromagnetic prospecting, low frequency A.C. is preferred as it provides better depth penetration of the electromagnetic fields.

Answer 1

The Correct Option is B

In electromagnetic prospecting, the primary field is generated using an alternating current (A.C.) source, typically at low frequencies. The choice of low frequency allows better penetration of the electromagnetic waves into the ground.
- Option (A): High frequency A.C. is not commonly used because higher frequencies tend to attenuate faster in the ground.
- Option (B): Low frequency A.C. is the correct choice, as it is commonly used in electromagnetic methods for subsurface exploration.
- Option (C): Both high frequency A.C. and D.C. are not typically used together for generating the primary field.
- Option (D): Low frequency D.C. is not suitable for electromagnetic methods, as D.C. does not generate the changing magnetic fields required for this method.
Thus, low frequency A.C. is the correct choice.