An electric field of 300 V/m is confined to a circular area 10 cm in diameter. If the field is increasing at the rate of 20 V/m-s, the magnitude of magnetic field at a point 15cm from the center of the circle will be:
Answer & explanation
Correct answer: option 4
$ B = \frac{\mu_0 \epsilon_0}{2\pi R}\frac{\pi d^2}{4} \frac{dE}{dt} = \frac{2\times 10^{-7}\times 8.85\times 10^{-12} 3.14\times 0.01\times 0.20}{4\times 0.15} = 1.85\times 10^{-18}T$