An engineer in a marine research laboratory is testing a new uniform copper-alloy umbilical cable designed for deep-sea sensors. They set up a test circuit using a safety-regulated 4.5 V4.5\text{ V}4.5 V DC power supply, an ammeter, a voltmeter, and a sample length of the alloy cable.
Explain why a 4.5 V4.5\text{ V}4.5 V power supply does not present an electrical shock hazard to the laboratory engineer.
At a cable sample length of 1.50 m1.50\text{ m}1.50 m, the current flowing through it is 0.75 A0.75\text{ A}0.75 A and the measured potential difference across this section is 3.6 V3.6\text{ V}3.6 V. Calculate the electrical resistance of this 1.50 m1.50\text{ m}1.50 m length of cable.
Assuming the temperature of the alloy cable remains constant, use the direct proportionality between the cable's length and its resistance to predict the resistance of a 4.50 m4.50\text{ m}4.50 m length of the same cable.