A 0.67 V potential difference is maintained across a 1.2 m length of tungsten wire that has a cross-sectional area of 0.45 mm2 . What is the current in the wire? The resistivity of the tungsten is 5.6 × 10−8 Ω · m . Answer in units of A.

To solve this problem we will apply the concepts related to Ohm's law, described as the equivalence between the voltage and the product between the current and the resistance. At the same time we will use the concept related to the electrical resistance as a function of the characteristics of the wire to finally find the current.

Ohm's law given by the following expression

The electrical resistance of a wire would be,

Here,

= Resistivity of the material

l = Length

A = Cross-sectional area,

Replacing the value of the Resistance and Ohm's equation we have,

Now rearranging to find the current

Our values are given as,

Replacing,

Therefore the current in the tungsten wire is 4.4866A

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.

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