HVAC Yr 2 Electrical
Electrical shock occurs when a person:
a. touches a live electrical conductor that is making contact with a ground Electricity for Refrigeration, Heating and Air Conditioning , 9th ed. pg. 3 Electricity for Refrigeration, Heating and Air Conditioning, 10th ed. pg. 3
R1 = 80 ohms, R2 = 100 ohms, and R3 = 400 ohms and the applied voltage = 120 volts. What is the voltage dropped across R-1?
a. 60 volts
One horsepower is equal to:
a. 746,000 milliwatts b. 746 watts c. 0.746 k watts d. all of the above are correct
Calculate the total resistance of all the lights in the circuit above. 12 VDC 1.5 A 5 resistors
a. 8 ohms
Calculate the voltage drop at R-4 using ohm's law and the series circuit rules handout.
a. 80 volts
Convert 0.81 M ohms into k ohms using the engineering notation handouts.
a. 810 K ohms
The smallest particle of an element that can exist alone or in combination is an:
a. atom
In the above drawing, if the voltage indicated was applied and each lamp was rated for 12 volts DC, they would:
a. burn normally (WRONG) Electricity for Refrigeration, Heating and Air Conditioning, 10th ed. pg. 46
A combination series/parallel circuit is a circuit that contains:
a. components wired in both series and parallel
Most metals easily give up free electrons from their outer orbit and therefore make good:
a. conductors
In a basic electric circuit with a fixed resistance, when voltage increases:
a. current increases
The term open and closed are used to describe switch positions. When a switch is closed:
a. current may pass through the switch
Electric current that flows in only one direction is called:
a. direct current
The flow of electrons in a circuit would be a definition of:
a. electrical current
In the Ohm's law relationship, if resistance is decreased and voltage remains the same current will:
a. increase
All physical objects are composed of:
a. matter
Electrons are:
a. negatively charged particles that orbit around the outer part of the atom
Receptacles used on construction job sites should be protected with:
a. portable GFCI circuit breaker
A positvely charged particle that exists in the nucleus of an atom would be a (an):
a. proton
The HVAC circuit shown above is an example of:
a. series-parallel circuit combinations
The first step in solving combination series/parallel circuits is to:
a. simplify the parallel block to match the series components (WRONG)
In a combination series/parallel circuit, to identify which paths are series and which paths are parallel, you should:
a. trace the path the current takes
What is electromotive force?
a. voltage b. electrical pressure c. electrical potential d. all of the above are correct
The basic Ohm's law formula is a mathematical equation that describes the relationship between:
a. volts, amps, and ohms
An electrical current flow through the human body of ____________ amps or less can prove fatal.
b. 0.015
Calculate the power of a circuit in watts with 250 Ohms of resistance and 120 applied volts.
b. 0.48 watts (WRONG) Electricity for Refrigeration, Heating and Air Conditioning 10th Ed., pg. 34
Calculate the current draw of a circuit with 1.5 K Ohms of resistance and 100 applied volts using Ohm's law. I = E/R
b. 0.667 amps Electricity for Refrigeration, Heating and Air Conditioning 10th Ed., pg. 34 Engineering Notation Handout
R1 = 80 ohms, R2 = 100 ohms, and R3 = 400 ohms and the applied voltage = 120 volts. What is the current flow through R-1?
b. 0.75 amps
What is the current draw of a 1200 W electric heater operating on a 120 volt AC power supply?
b. 1200 watts / 120 volts = 10 amps
Calculate the total voltage drop in the circuit using ohm's law and the series circuit rules handout. (VIRP) 4 resister R-1 = 1 K ohm R-2 = 500 ohm R-3 = 10 V R-4 = 2 k ohm Current = 40 mA
b. 150 volts
Calculate the voltage drop across each lamp assuming they are all the same type and resistance. 12VDC 1.5A 5 resisters
b. 2.4 volts
Calculate the total resistance of a series circuit containing 4 resistors of the following values:500 ohm, 25 k ohm, 1.5 k ohm, and 2.5 k ohm.
b. 29.5 k ohms
Calculate the electric power for a 12 volt DC circuit drawing 3 amps?
b. 3 amps x 12 volts = 36 watts
Convert 480,000 ohms into k ohms using the engineering notation handouts.
b. 480 k ohms
R1 = 240 ohms, R2 = 300 ohms, and R3 = 1200 ohms. What is the total resistance of the circuit?
b. 480 ohms
Convert 0.005 milliamps into microamps using the engineering notation handouts.
b. 5 uA
An electric circuit without a complete path for current to flow is called:
b. an open circuit
A switch controls the flow of electricity by:
b. closing the current when it is turned on and opening the circuit when it is turned off
To solve the combination circuit shown above you would have to do which of the following?
b. convert R-2 and R-3 into a series circuit
The rate at which electrons do work would be a definition of:
b. electrical power
What part of the components that make up an atom can travel from one atom to another?
b. electron
What are free electrons?
b. electrons that are easily knocked out of their orbits
In a series circuit, the voltage dropped across each load is:
b. equal to the applied voltage (WRONG) Electricity for Refrigeration, Heating and Air Conditioning, 10th Ed. pg. 46 and Series Circuit Rules Handout
In a series circuit, the voltage dropped across each load is:
b. equal to the applied voltage when added together
Materials whose atoms do not easily give up or take on electrons are called?
b. insulators
A (An) ____________ is the smallest particle of a substance that has the properties of that substance.
b. molecule Electricity for Refrigeration, Heating and Air Conditioning 10th Ed., pg. 21
Control devices in an electrical HVAC circuit are connected in _____________ with the load.
b. series
An electric furnace has three heating elements that have a resistance of 12 Ohms each. The applied voltage to the elements is 240 volts. What is the wattage rating of each element in Kw?
c. 2.88 kw (WRONG) Electricity for Refrigeration, Heating and Air Conditioning 10th Ed., pgs. 32 & 36
Convert 0.000025 amps into microamps using the engineering notation handouts.
c. 25 microamps
Calculate the total current in the circuit above.
c. 26.25 amps
What is the voltage drop across a 30 ohm resistor with a current draw of 5 amps?
c. 30 ohms x 5 amps = 150 volts
Calculate the total power used in the circuit using ohm's law and the series circuit rules handout. (VIRP) 4 resister R-1 = 100 ohm R-2 = 50 v R-3 = 200 ohm R-4 = 500 ohm Current = 50 mA
c. 4.5 watts
Convert 0.000005 amps to microamps.
c. 5 microamps
Convert 0.005 milliamps to microamps.
c. 5 microamps
Convert 57,000,000 watts to Megawatts.
c. 57 Megawatts
Convert 65,000 ohms to k ohms.
c. 65 k ohms
An electrical device that will open an electrical circuit if a small current leak to ground occurs would be a:
c. GFCI circuit breaker
Which of the following terms is NOT used to describe electrical pressure?
c. current
The induction method of producing electron flow uses which of the following means to produce electricity?
c. friction (WRONG) Electricity for Refrigeration, Heating and Air Conditioning 10th Ed., pg. 26
In an electrical circuit, the direction of electron flow is:
c. from a negative charge to a positive charge
The flow of electrons caused by friction would be a definition of:
c. static electricity
An ampere is:
c. the amount of current required to flow through a resistance of 1 ohm with a pressure of 1 volt
In a series circuit, the total current flow is:
c. the same throughout the circuit
The total current in a series circuit is
c. the same throughout the circuit
To find the watts of electrical power in an electrical circuit, you multiply:
c. volts and amperes
Convert 500 milliamps to amps.
d. 0.5 amps
R1 = 80 ohms, R2 = 100 ohms, and R3 = 400 ohms and the applied voltage = 120 volts. What is the current through R-2?
d. 1.2 amps (WRONG) Step 1: Calculate the total resistance of R2 and R3 in parallel using the reciprical formula.Step 2: Replace resistors R2 and R3 with ONE resistor whose value equals the calculated value in step 1. Now you have a series circuit.Step 3: Calculate the total resistance of the circuit by adding the value of both resistors in series. Step 4: calculate the total current of the circuit by dividing the applied voltage by the total resistance. This is the current through R1.Step 5: Calculate the voltage drop across R1 by multiplying the current through R1 times the resistance of R1. This is the voltage drop at R1. (0.75 amps x 80 ohms = 60 volts)Step 6: The voltage drop at R2 and R3 is calculated by subtrating the voltage drop at R1 from the applied voltage. This is the same for both R2 and R3 since they are in parallel.Step 7: Calculate the current through R2 by dividing the voltage drop at R2 by the resistance of R2.
Convert 10 amps to milliamps
d. 10,000 milliamps
What is the voltage of a small electric heater that is drawing 12 amps and has a resistance of 10 ohms?
d. 120 volts
An electric furnace has three 5 Kw heating elements. Calculate the total Btu output of the furnace? 1 watt = 3.41 Btu/hour
d. 17,065 Btu's (WRONG) Electricity for Refrigeration, Heating and Air Conditioning 10th Ed., pg. 32
Convert 2,700,000 watts into megawatts using the engineering notation handouts.
d. 2.7 Mw
What is the amp draw of a 5 kw electric heater with an applied voltage of 120 volts?
d. 42 amps
Calculate the voltage drop at R-1 using ohm's law and the series circuit rules handout.
d. 5 volts
Convert 75 M ohms to k ohms.
d. 75,000 k ohms
Calculate the total voltage drop in the circuit using ohm's law and the series circuit rules handout.
d. 90 volts
The three essential requirements for a useful electric circuit are:
d. A power source, a path for current flow, and an electrical load
Most HVAC/R systems operate on
d. Alternating current (AC)
In refrigeration and air conditioning, switches are normally wired:
d. In series with the load they control
Electric current that regularly reverses flow is called:
d. alternating current
Two 115 volt light bulbs connected in series with 230 volts would:
d. burn correctly
Materials whose electrons can be easily knocked out of their atomic orbits, creating free electrons, are called?
d. conductors
In an electrical circuit, the direction of electron flow is:
d. from a negative charge to a positive charge
An material that does not easily give up or take on electrons, but actually resists the flow of electrons would be a (an):
d. insulator
Which of the following is true according to the law of electrical charges?
d. like charges repel and unlike charges attract
The center section of an atom is composed of which of the following?
d. protons (WRONG) Electricity for Refrigeration, Heating and Air Conditioning 10th Ed., pg. 22
Solving combination series/parallel circuits requires you to:
d. reduce the circuit to a simpler circuit either series or parallel
The opposition to the flow of electrons in an electric circuit, is the definition of which of the following electrical characteristics?
d. resistance
What three elements are required for all electric circuits?
d. source, path, and load
In a combination series/parallel circuit, to identify which paths are series and which paths are parallel, you should:
d. trace the current paths
What is the Btu/hr output of an electric heater rated at 15 Kw? 1 watt = 3.41 btu/hr
d.51.15 Btu/hr (WRONG) Electricity for Refrigeration, Heating and Air Conditioning , 9th ed. pg. 34 Electricity for Refrigeration, Heating and Air Conditioning, 10th ed. pg. 32
Typical insulators are:
glass, rubber, plastic
What is the kw output of an electric heater that is drawing 50 amps with 120 volts applied?
a. 6 kw
Convert 0.010 amps into milliamps using the engineering notation handouts.
10 mA
The current flow through R-3 in the circuit above would be:
20 milliamps
R1 = 80 ohms, R2 = 100 ohms, and R3 = 400 ohms and the applied voltage = 120 volts. What is the voltage across R-2?
a. 60 volts
Electrical shock and burns are common hazards to personnel who are employed in the HVAC or electrical industry only.
False
Series and parallel circuits have the same relationships of voltage, amperage and resistance.
False
What is the current draw of a 120 volt circuit with a resistance of 20 ohms?
a. 120 volts / 20 ohms = 6 amps
Calculate the total resistance of a series circuit containing 4 resistors of the following values : 100 ohms, 25 k ohms, 1.5 k ohms, and 2.5 k ohms.
a. 29.1 k ohms
Calculate the total resistance of the circuit using ohm's law and the series circuit rules handout. (VIRP) 4 resister R-1 = 1 K ohm R-2 = 500 ohm R-3 = 10 V R-4 = 2 k ohm Current = 40 mA
a. 3.75 k ohms