NATE Air Conditioning and Heat Pumps Practice Exam

As the length of electrical wire increases, its resistance ____ while the temperature is maintained at a constant level.

1. decreases

2. increases

3. remains unchanged

4. varies unpredictably

The correct answer is: increases

As the length of electrical wire increases, its resistance increases due to the inherent properties of conductive materials. Resistance in a conductor is directly proportional to its length; this means that the longer the wire, the more material the electric current has to pass through, leading to additional collisions between the electrons (current) and the atoms in the wire. This concept is grounded in Ohm's Law and the formula for resistance, which states that resistance is equal to the resistivity of the material multiplied by the length of the conductor and divided by its cross-sectional area. When keeping the temperature constant, the resistivity of the conductor does not change, so any increase in length will directly result in a proportional increase in resistance. Thus, this relationship confirms that as the length of the wire increases, resistance does indeed increase.