Astudent makes a short electromagnet by winding 300 turns of wire around a wooden cylinder of diameter d= 5.0 cm. the coil is connected to a battery producing a current of 4.0 a in the wire what is the magnitude of the magnetic field a distance of 20.0 cm from the center of this device?

0.19 m/s and 0.45 m/s

where’s the list ? the question is incomplete

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.