The Biot-Savart law gives the magnetic field dB at a point due to a current element Idl as:
AdB = μ₀I dl sinθ / 4πr
BdB = μ₀I dl sinθ / 4πr²
CdB = μ₀I dl / 4πr²
DdB = μ₀I dl cosθ / 4πr²
Question 2
The magnetic field at the centre of a circular coil of radius R carrying current I (N turns) is:
AB = μ₀NI/R
BB = μ₀NI/2R
CB = μ₀NI/4πR
DB = 2μ₀NI/R
Question 3
Ampere's circuital law states that ∮B·dl around a closed loop equals:
AZero always
Bμ₀ × (enclosed current) = μ₀ I_enclosed
CThe total magnetic flux through the loop
Dμ₀ε₀ dΦ_E/dt only
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