Two circular coils are made from a uniform wire the ratio of radii of circular coils are `2:3 &` no. of turns is `3:4` . If they are connected in parallel across a battery.
`A:` Find ratio of magnetic inductions at their centres
`B:` Find the ratio magnetic moments of 2 coils.

Explanation

When connected in parallel
a ) `B prop (1)/(r^2) , B_1/B_2 = (r_2/r_1)^2 = (3/2)^2 = 9.4`
b) ` M = "ni"A_("coil") " but" i = V/R = (V)/(rho l) A_("wire")`
` rArr M = (Va_("wire"))/(rho(2pir_("coil") )) (pir_("coil")^2) , M = (VA_("wire") )/(rho xx 2) r_("coil")`
`M_1/M_2 = r_1/r_2 = 2/3`