Flashcards in Electrical Deck (23)
What are the two types of electric circuits in a home?
Power circuits (house voltage) - heat, light, motion
Control circuits (low voltage) - regulate furnaces, water heaters, and appliances
A circuit is composed of three parts:
Source (power plant), path (wires), load (device)
Switches are used to:
open and close a circuit
Have only on continuous path
Voltage drops across each load
Not used to connect multiple loads
Have multiple paths, each containing a load
Most home circuits are wired in parallel to ensure consistent voltage to all loads
Control circuits provide precise control of energy systems. What are their components?
Transformer - reduces voltage down to 24V
Controller - sense environmental conditions or user input
Control element - pump, gas valve, burner, fan, etc
What is Ohm's Law?
E = I x R
Voltage = Current x Resistance
What is voltage?
Electrical pressure or force measured in volts
What is current?
Flow of electrons measured in amps
What is resistance?
Opposition to current flow measured in Ohms. Produces work
What's the Power Law?
Current x Voltage = Power in Watts
Describe how electricity gets from power lines to a house.
Service drop extends from the utility pole to the electrical meter of the house (2 120 V hot wires, one neutral structural wire).
Feeder wires connect the meter to the panel box.
A grounding wire connected to the panel metal is connected to the neutral feeder and attached to a copper grounding rod driven into the ground.
What are the two types of circuits in a house?
Branch circuits - serve multiple loads such as lights, fans, outlets, etc.
Appliance circuits - serve a single appliance each like refrigerator, water heater, heating system, etc.
What's a short circuit?
The flow of electricity through a circuit that does not contain a load or contains a very low resistance load. When resistance drops near zero, max current is produced.
Short circuits occur because of:
Sticking something in an outlet, disconnected wiring, worn insulation, damaged cords, etc
A branch circuit wired with 12-2 wire should have a max ___ amp breaker that protects the wire from overheating if too much current flows.
Circuits wired with 14-2, or older house branch circuits, should have a max ___ amp breakers.
What's a fault circuit?
The accidental flow of electricity through a stray circuit that is not part of the electrical system of the house. Common in presence of water.
What's a GFCI?
A Ground Fault Circuit Interrupter protects outlets in wet locations. It trips instantly if it detects any mismatch in current between the hot wire and the neutral wire, indicating a fault.
What's the top left hole in an outlet?
What's the top right hole in an outlet?
What's the lower center hole in an outlet?