A 60-Watt bulb illuminates a surface a distance d away with
an illuminance of 3600 lux. What would be the illuminance
on a surface a distance 0.5•d away (i. e., one-half the
distance away) when illuminated by a 120-Watt bulb?

Explanation:

Relation between power and illumination and distance  is as follows

For first  case

for second case

I = 3600 x 8

= 28800 lux .

a solenoid is created by wrapping a l = 90 m long wire around a hollow tube of diameter d = 4.5 cm.   the wire diameter is d = 0.9 mm.   the solenoid wire is then connected to a power supply so that a current of i = 9 a flows through the wire.

randomized variablesl = 90 m

d = 4.5 cm

d = 0.9 mm

i = 9 a                                          

write an expression for the number of turns, n, in the solenoid. you do not need to take into account the diameter of the wire in this calculation.

calculate the number of turns, n, in the solenoid.

write an expression for the length of the solenoid (l2) in terms of the diameter of the hollow tube d.

calculate the length of the solenoid (l2)   in meters.

calculate the magnitude of the magnetic field at the center of the solenoid in teslas.

explanation:

it takes about 30 days for it to break down