If a rubber jumper is rated for 300 amps, what is the potential increased rating when doubled?

When a rubber jumper is rated for 300 amps, this rating reflects the maximum current the jumper can safely carry without overheating or failing. Doubling the rating implies that if you have two jumpers, each rated at 300 amps, and you use them in parallel, the total capacity would effectively increase.

When two equal-rated conductors are combined in parallel, their current ratings add together. Therefore, if you have two rubber jumpers rated at 300 amps each, when used together, the combined rating is simply the sum of their individual ratings: 300 amps + 300 amps equals 600 amps.

Thus, the potential increased rating when the jumper's capacity is doubled is indeed 600 amps, making it the correct answer. This principle is crucial in electrical work, as it ensures safety and compliance with the necessary electrical codes and standards.