Answer:

Explanation:
The magnetic dipole moment of a circular coil with a current is given by
where
I is the current in the coil
is the area enclosed by the coil, where
is the radius of the coil
So the magnetic dipole moment can be rewritten as
(1)
Here we can assume that the magnetic dipole moment of Earth is produced by charges flowing in Earth’s molten outer core, so by a current flowing in a circular path of radius

Here we also know that the Earth's magnetic dipole moment is

Therefore, we can re-arrange eq (1) to find the current that the charges produced:

Answer:
Explanation:
Radius of ring r = .05 m
Electric field due to a uniformly charged ring
E = k Q x / ( x² + r² )³/² ; Q is charge on the ring , x is distance of point from the center of the ring and r is radius of the ring
electric field due to first ring at middle point or at x = 7.5 cm
E = 9 x 10⁹ x 33 x 10⁻⁹ x 7.5 x 10⁻² / ( 7.5² + 5² )³/² x 10⁻³
= 9 x 10⁹ x 33 x 10⁻⁹ x 7.5 / ( 7.5² + 5² )³/² x 10⁻¹
= 9 x 10⁹ x 33 x 10⁻⁹ x 7.5 / 73.23
= 30.41 N/C
The same field will be created by the other ring at the middle point because charge on the ring is same in magnitude . Due to negative charge on the second ring , field due to both the rings will align in the same direction.
Total field = 2 x 30.41
= 60.82 N/C
A. One substance must dissolve in another