An 800 kHz radio signal is detected at a point 3.2 km distant from a transmitter tower. The electric field amplitude of the signal at that point is 320 mV/m. Assume that the signal power is radiated uniformly in all directions and that radio waves incident upon the ground are completely absorbed. The magnetic field amplitude of the signal at that point, in nT, is closest to:

1.07 nT

Explanation:

We know that E/B = c where E = electric field amplitude = 320 mV/m = 0.32 V/m, B = magnetic field amplitude and c = speed of light = 3 × 10⁸ m/s.

So, B = E/c

Substituting E and c into B, we have

B = E/c

= 0.32 V/m ÷ 3 × 10⁸ m/s

= 0.1067 × 10⁻⁸ T

= 1.067 × 10⁻⁹ T

= 1.067 nT

≅ 1.07 nT

the higher the current the higher the mag field around it the higher the influence on the compass