As more lamps are put into a series circuit, the overall current in the circuit a. increasesb. decreasesc. remains the same

b. Decreases

Explanation:

The total resistance of a series circuit is equal to the sum of the individual resistances:

(1)

Therefore, as we add more lamps, the total resistance increases (because we add more positive tems in the sum in eq.(1).

The current in a circuit is given by Ohm's law:

where V is the voltage provided by the power source and is the total resistance. We notice that the current, I, is inversely proportional to the total resistance: therefore, when more lamps are added to the series circuit, the total resistance increases, and therefore the current in the circuit decreases.

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.