Question

A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has its north tip pointing down at ${22}^0$ with the horizontal. The horizontal component of the earth's magnetic field at the place is known to be $0.35G$. Determine the magnitude of the earth's magnetic field at the place.

• A. 0.12
• B. 1.23
• C. 4.56
• D. 0.38

Answer 1

The correct option is D 0.38

$WehorizontalcomponentofearthmagneticfieldH=Rcos\theta Where\theta =angleofdip={22}^{0}andthevalueofH=0.35GSoputtingthevaluesrespectivelyR=\frac{H}{cos\theta }=\frac{0.35}{cos22}=\frac{0.35}{0.927}=0.377=0.38G$