Answer:
636.619772368 A
Explanation:
= Torque = 
B = Magnetic field of Earth = 
A = Area
d = Diameter = 20 cm
Current is given by

The current is 636.619772368 A
Rate of speed (3 m/s north is three miles per second north, so it's a rate of speed)
Answer:
Tension in string equals 14.715 Newtons
Explanation:
The situation is represented in the figure attached below:
For equilibrium of the clothes along y- axis we have

Applying values we get

Answer:
(1) By increasing the number of loops of wire around the iron core
(2) increasing the current or voltage.