How large an expansion gap should be left between steel railroad rails if they may reach a maximum temperature 30.0°C greater than when they were laid? Their original length is 30.0 m.

1.2 cm

Explanation:

Thermal Expansion

It's the tendency that materials have to change its size and/or shape under changes of temperature. It can be in one (linear), two (surface) or three (volume) dimensions.

The formula to compute the expansion of a material under a change of temperature from to is given by.

Where Lo is the initial length and is the linear temperature expansion coefficient, which value is specific for each material. The data provided in the problem is as follows:

Computing the expansion we have

The expansion gap should be approximately 1.2 cm

the current is 0.6

voltage ÷ resistance = current

so 12 ÷ 20 = 0.6

luster is not a good characteristic to use by itself because luster is the property of minerals that indicates how much the surface of a mineral reflects light. the luster of a mineral is affected by the brilliance of the light used to observe the mineral surface.