Answer:
M = 1.98g
Explanation:
Please see the attachment below.
For the mass to balance the force of repulsion, the gravitational force on the mass (its weight) must equal the magnetic force of repulsion between the straight rods.
So
Mg = μo ×I ×I' × L/2πr
M = μo ×I ×I' × L/2πrg
Given
I = I' = 18A
L = 60cm = 0.6m
r = 2mm = 2×10-³m
μo = 4π×10-⁷Tm/A
g = 9.8m/s²
M = (4π×10-⁷ × 18² × 0.6)/(2π×2×10-³ ×9.8) = 1.98 ×10-³ kg.
