The main idea is how current, voltage, and power relate on a circuit. A device that uses 1200 watts at 120 volts draws current I = P / V = 1200 / 120 = 10 amperes. A 20-amp circuit breaker can supply up to 20 amperes, so you can run up to two of these dryers at the same time (2 × 10 A = 20 A). Three would require 30 amperes, which would trip the breaker. In practice, startup surges can affect current, but the straightforward calculation shows two is the limit for this setup.

Total resistance is found by simplifying the network using series and parallel rules. In this circuit, resistors are arranged so that a pair is in parallel, and that parallel combination sits in series with another resistor. You first find the parallel equivalent: if the two resistors are 10 Ω and 30 Ω, their parallel result is Rp where 1/Rp = 1/10 + 1/30 = 4/30, so Rp = 7.5 Ω. Then you add the resistor in series with that parallel group: 7.5 Ω + 7.5 Ω = 15 Ω. So the total resistance comes out to 15 Ω. The other numbers would come from using different combinations or misidentifying the series/parallel relationships.

Systematic troubleshooting in electrical problems is a structured, data-driven process that prevents guesswork. It starts by defining the problem clearly and identifying its scope, then gathering data such as symptoms, measurements, and operating conditions. With this information, you establish a theory about the likely cause and design tests to validate or refute that theory. If the tests support the theory, you implement a fix and then verify that the issue is resolved under normal operation and that no new problems were created. Finally, you document the problem, the steps taken, the results, and the final solution for future reference. That sequence is best because it relies on evidence and repeatable checks to confirm the root cause before making changes, ensures the fix actually resolves the issue, and creates a record for future maintenance. Options that skip testing, guess-and-replace components, or verify a solution before clearly defining the problem violate this logical, methodical approach and can lead to unresolved issues or repeated failures.

Insulation resistance testing with a megohmmeter checks how well the insulation resists leakage by applying a high DC voltage to the insulation and measuring the leakage current to compute resistance. The aim is to reveal insulation deterioration, moisture, or contamination that would lower resistance and threaten reliability. A high resistance value means the insulation is still doing its job effectively, indicating good health; a low value flags problems that may require maintenance or repair. This test specifically targets insulation between conductors and earth or between different conductors, not the resistance of the conductors themselves. It doesn’t assess mechanical wear or articulation of moving parts, and it isn’t used to estimate operating temperature. For a complete picture, technicians consider insulation resistance alongside proper test voltage, ambient conditions, and sometimes indices like the polarization index to track how resistance changes over time.