Answer:
9 cm
-36 cm
Explanation:
u = Object distance
v = Image distance
f = Focal length = 12
m = Magnification = 4

Lens equation

Object distance is 9 cm

Image distance is -36 cm (other side of object)
Answer:
The magnetic force on the section of wire is
.
Explanation:
Given that,
Current 
Length = 0.750 m
Magnetic field 
We need to calculate the magnetic force on the section of wire
Using formula of magnetic force


Since, 

Hence, The magnetic force on the section of wire is
.