Electrical components final exam
100 milliamps
.1 amps
Relays used in the HVAC industry are generally used to control loads up to
10 amps
The synchronous speed of a 4 pole 60 hertz single phase motor is
1800 RPMs
2.1 kv
2100 volts
Utility companies usually provide residential homes with _______ service
240 volts single phase 3 wire
1 horsepower equals
746 Watts
Overcurrent can be caused by
A Ground-fault an overloads or a short circuit
A _______may be used on a single phase induction motor to disconnect the start winding after the motor starts
A centrifugal switch an amp relay or a potential relay
Any material that will gradually release electrons
A conductor
An ohmmeter should never be connected to
A live circuit
An electron has
A negative charge
A device used to control a motor is
A relay a contactor or a line starter
In a series circuit the voltage drop across each load will
Add up to equal The Source voltage
When checking the windings of a 3-phase motor
All three terminals should show the same resistance
How are fuses sized
Amps and volts
What meter is used to bench check
An ohmmeter
What meter uses its own battery
An ohmmeter
The terminals T1 T2 and T3 are located at the _______ of a contactor
Bottom
To change the direction of rotation of a 3-phase motor
Change the position of any two Supply wires
Contactors are rated according to the maximum amperage through the
Contacts
A solenoid valve operates on the principle of
Electromagnetism
A 240 volt 3 wire circuit can be split into two 120 volt circuits
False
A thermocouple can
Generator small electrical current depending on the temperature
With the motor running at full load voltmeter leads are placed on each side of the relay contacts the voltmeter gives no measurable voltage this is an indication of
Good clean contacts
Electricity can produce
Heat light and magnetism
The symbol for current is
I
Capacitors are always connected __________ to the start winding
In series
When the temperature of a positive temperature coefficient thermistor increases
It's resistance will increase
The total resistance of a parallel circuit will be
Less than the smallest resistance
When current flows a ________ is produced around the conductor
Magnetic field
The thermal overload contacts online starter are usually reset
Manually
Capacitors are rated in
Microfarads and volts
Are single phase Motors more efficient than three phase Motors
No
If a safety ground shows a thousand ohm continuity to the motor frame is it a good safety ground
No
If contacts become dirty or pitted is it acceptable to Sand or file them as a permanent repair
No
Impedance
Opposition to alternating current flow
Resistance is
Opposition to current flow
The _______ drawing illustrates where the components are located on the appliance
Pictorial
A transducer can create a signal based on a form of energy such as
Pressure Heat or fluid flow
The capacitor start capacitor run motor
Provides High start and run torquex
Like charges
Repel each other
In a single phase motor which winding has the most resistance
Start winding
Direction of rotation of a single phase induction motor is determined by
The direction of current flow through the start winding
Current flow
The flow of electrons in the circuit
A single phase motor speed is determined byA single phase motor speed is determined by
The number of stator poles
When the temperature of a negative temperature coefficient thermistor increases
The resistance will decrease
The output side of a transformer isThe output side of a transformer is
The secondary side
A three-phase system requires a minimum of three supply lines to the three phase load
True
How many switches can be connected to a contactor coil control circuit
Unlimited
How to discharge a capacitor prior to Ohmmeter testing
Use a 20000 Ohm resistor To short across the terminals
When replacing a capacitor
Use a duplicate, microfarads equal, never under capacitance
Transformers are rated according to
VA at the primary
A Step up Transformer increases
Voltage
The meter on a house measures
Wattage
Fuses are used to protect
Wires
