Comprehensive Electrical HVAC Test Questions and Answers, A+

What is electricity? - Flow of electrons between atoms in common wire material or load What is current flow? - Electrons flow What creates a magnetic field in a conductor? - Current flow What is voltage? - Electrical pressure that pushes current flow What is the difference between a conductor and an insulator? - A conductor allows current flow. What are the two common types of electricity? - Direct current and alternating current What is control voltage? - The electrical section of the HVACR system that manages the on and off cycles What is resistance? - Resistance is the force that slows down the flow of electrons in a circuit. What is a watt? - The rate of doing work or power What is a meant by a load? - Any component that has a resistance to electron or current flow What is the Ohm's law formula? - E = I × R What is Watt's formula? - W = I × E What is the formula for finding resistance? - R = E / I How many volts will be measured with an amp draw of 10A and a resistance of 20 Ω? - 200 volts How many amps will be measured in a circuit with 120V and a resistance of 20Ω? - 6A How much resistance will be measured in a circuit with 240V and amp draw of 10A? - 24Ω How many watts will be measured in a circuit with 240V and 10A? - 2400 watts How many watts will be measured in a circuit with 480V and 10A? - 4.80 kW Ohm's law is valid - with resistive loads only. What is another term used for the watt? - Power What is the total resistance of 3 resistors wired in series? Each has a resistance of 10Ω - 30Ω What is the total resistance of 3 resistors wired in parallel? Each has a resistance of 10Ω - 3.3Ω What is the total resistance of 4 resistors wired in parallel? There are two 20Ω resistors and two 40Ω resistors. - 6.67Ω What is the total resistance of a combination circuit that has a 10Ω resistor in series with two parallel 10Ω resistors? - 15Ω You measured the resistance of a 4,000-watt heat strip that has a resistance of 18 ohms. How many amps would you expect to measure when the heat strips are energized? - 15 amps Regarding safety, what is the difference between high voltage and low voltage? - High voltage can kill immediately. Low voltage (120V) can cause bodily damage not realized until a day later.