Question

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The speed of light is _____ km/s.

Answer 1

Hint: The speed of light, denoted by c is a universal constant. One must know it's value in meters per second and then convert it to kilometers per second to obtain the correct answer for the blank.

Complete step by step answer:
The distance that the light is known to travel in 1 second in vacuum is 299,792,458 meters to be precise. The speed of light in vacuum is famously known constant with a value given by:
$c=3\times {10}^8$m/s.
In km/s we may write:
$c=3\times {10}^5$ km/s.

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

Additional information:
Speed of light remains the same in different inertial frames. This is a fundamental postulate in the theory of special relativity given by Einstein. Inertial frame is a frame which undergoes constant motion and is not affected by external force. Also it is a fact that nothing can achieve a speed greater than the speed of light. Speed of light is an upper limit for the motion of any physical entity in this universe as far as we know. The speeds that are closer to the speed of light are treated differently and the whole mechanics at such speed shifts to relativistic mechanics instead of usual classical laws. Some subatomic particles have been able to achieve speeds that are very close to the speed of light but not yet exactly c.

Note:
It should be noted that in the expression for the heat energy, the amount of heat energy depends on the square of the electric current passed through the conductor while there is linear dependence on the resistance of the conductor. This means that we will get greater heating when we vary the current through the conductor rather than resistance.