A light-year is a unit of distance.
The definition of a light-year is the distance light travels in one year.
zero.
from newton's first law of motion
It is fairly easy to build an electromagnet. All you need to do is wrap some insulated copper wire around an iron core. If you attach a battery to the wire, an electric current will begin to flow and the iron core will become magnetized. When the battery is disconnected, the iron core will lose its magnetism. Follow these steps.
Step 1 - Gather the Materials
One iron nail fifteen centimeters (6 in) long
Three meters (10 ft) of 22 gauge insulated, stranded copper wire
One or more D-cell batteries
Step 2 - Remove some Insulation
Step 3 - Wrap the Wire Around the Nail
Step 4 - Connect the Battery
Torque acting dowward = 6 x 0.5 = 3 Nm
Torque acting to the right = 5 x 1 = 5 Nm
5 - 3 = 2 Nm
inertia = 1/2 mr^2
0.5 x 10 x 1^2 = 5 kg-m^2
2/5 = alpha = 0.4 rad /s^2
Hope this helps
