Esco Electrical Test

What amperage measurement would you expect if you clamped your meter around both wires in a two wire circuit?

0 due to the cancellation of the two magnetic fields

Which of the following is equal to 100 milliamps?

0.10 amps

What is the minimum number of wires required between two start/stop push button controls?

1

Three 300 ohm resistors are wired parallel. What is the total resistance?

100 ohms

How much resistance must be placed in a 120 volt circuit to limit the current to 2 amps?

120ohms

The voltage to ground of a "high leg " or stringer leg" on a three phase open Delta system will be approximately.

208

The voltage to ground of a high leg or "stinger leg" on a three phase open delta system will be approximately:

208

Which of the following is equal to 2.1kW?

2100 watts

How many watts are used by a heater operating on 460 volts and drawing 5 amps?

2300

A transformer has 1000 turns on the primary side and 2000 on the secondary. What is the output if the input is 120v?

240v

Utility companies usually provide residential homes with:

240v, single phase, three wire

Three defrost heaters, each 15 ohms, are wired in parallel to a 120 volt power supply. How many Watts are consumed?

2880

Three resistors are wired parallel. Two have a value of 12 ohms, one of 6. What is the total resistance?

3

Which of the following is an acceptable temporary replacement capacitor for a 35MFD, 440VAC capacitor?

37.5MFD, 440VAC

What is generally considered the maximum allowable supply voltage variation

5%

A parallel circuit contains an 18 ohm and a 9 ohm resistor. What is the total resistance?

6 ohms

A parallel circuit consists of three resistors; R1 = 30 ohms, R2 = 15 ohms, R3 = 10 ohms. If the current through R2 = 4 amps, what is the source voltage?

60 volts

A transformer has 1000 turns on the primary side and 500 on the secondary. What is the output if the input is 120v?

60v

One horsepower is equal to ______ watts.

746

The symbol for a pressure switch that closes on a rise of pressure is represented by:

A

IN the schematic,(during operation ) what voltage would be found across the condenser fan motor?

A . 240 volts

Any material that will readily release electrons is called:

A conductor

When testing a motor with an ohmmeter, the following measurements are recorded; C to R = 4, C to S = 6.2, R to S = 10.2, R to ground = 20.4. This indicates:

A grounded condition

In electrical wiring, a black colored wire indicates:

A hot conductor

An electron has:

A negative charge

Ine the schematic, what voltage would be be found from terminal Y to the input side of the coil on the line #11? (Assume the thermostat is in the closed position and the fan is set to auto.)

A. 0 volts

IN the schematic, what voltage would be found across l1 to l2 ?

A. 240 volts

Amps can be calculated by:

A. E/R B.W/E C.The square root of W/R answer: D. all the above

In a series circuit, the voltage drop across each load will:

Add up to equal the source voltage

When checking the windings on a three phase motor, the resistance readings should:

All read the same

Electricity can produce:

All the above light heat magnetism

The symbol for a heating thermostat is represented by:

B

In the schematic, what voltage would be found (during operation) acros the contacts when energized in line #8? (Assume the thermostat is in the closed position and the fan is set to auto.)

B. 0 volts

In the schematic, what voltage would be found from termianl G to the load side of the transformer? (Assume the thermostat is in the closed position and the fan is set to auto.)

B. 24 volts

IN the schematic,(during operation ) what voltage would be found across the transformer primary

B. 240 volts

The symbol for a pressure switch that opens on a rise in pressure is represented by:

C

When troubleshooting a A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and the condenser fan motor are short cycling. The blower motor is not running . This could be caused by ?

C. A faulty blower motor or blower relay

When troubleshooting a A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and the condenser fan motor are not running. The blower motor is running . This could be caused by ?

C. The HP, LP, overloads, oil pressure switch are open

When troubleshooting the A/C system in the schematic, the following conditions are found. The thermostat contacts are closed. The compressor and condenser fan motor are short cycling. The blower motor is not running. When the fan switch at the thermostat is moved from the AUTO position to the FAN ON position the blower runs. This could be caused by:

C. a faulty thermostat- auto / fan on switch

In the schematic, the crankcase heater will operate;

C. when the compressor is off

To change rotation on a 3-phase motor:

Change position of any two wires

An ohmmeter should never be connected to a:

Charged capacitor until it has been discharged

Contactors are rated according to the maximum amperage through the:

Contacts

A diode is used to?

Control the direction of electron flow

Which of the following statements about current is true?

Current flow will increase when voltage increases

A ___ is commonly used on a single phase fractional horse power compressor to disconnect the start winding.

Current relay

The synchronous speed of a four pole, 60 Hz single phase motor is:

D. 1800 RPM

IN the schematic,, the coil on line # 11 does not control;

D. the blower motor

When the temperature of a negative temperature coefficient (NTC) thermistor increases, its resistance:

Decreases

Resistance can be calculated by:

E divided by I

Which of the following motors is most energy efficient?

ECM

Which of the following would be considered an inductive load?

Electric motor

A solenoid valve operates on the principle of:

Electromagnetism

Direct digital control (DDC) is:

Electronic controls used for equipment control and monitoring

A thermocouple can:

Generate a small DC current

With a motor running at full load, voltmeter leads are placed on L1 and T1 with no measurable voltage detected. This indicates:

Good, clean contacts

The safety ground conductor is usually colored:

Green and bare

The symbol for current is:

I

Capacitors are always connected _____ with the start winding?

In series

When the temperature of a positive temperature coefficient (PTC) thermistor increases, its resistance:

Increases

If the conductor in an AC circuit is wound into a coil, the resulting EMF opposes supply voltage. This is called:

Inductive reactance

Voltage can be calculated by:

IxR

The total resistance in a parallel circuit will be:

Less than the smallest resistance

A device with overload protection used to control a motor is a:

Line starter

What connects the T1, T2 and T3 terminals on a contactor?

Load wires

The thermal overload contacts on a line starter are usually ___ reset.

Manual

When testing a capacitor with an analog or digital ohmmeter, the meter should:

Measure low resistance then return to a high reading

Capacitor-start, capacitor-run motors provide:

Medium running and high starting torque

Capacitors are rated in:

Microfarads and volts

Single phase motor speed is determined by:

Number of stator poles

Which of the following meters must use internal power to check a load or circuit?

Ohmmeter

What would be the result if a 24 volt, 20 ohm contactor coil was wired in series with a 24 volt, 200 ohm control relay?

Only the control relay would operate

What is impedance?

Opposition to alternating current

What is resistance?

Opposition to electron flow

The ____ drawing illustrates where the components are located on the appliance.

Pictorial

The most common type of transducer used with HVAC/R equipment creates a signal based on:

Pressure

Circuit breakers and fuses are used to provide:

Protection from an overload of current

An electronically commutated motor (ECM) is designed to:

Provide proper airflow under various conditions

Like charges will

Repel each other

If contacts become badly pitted, it is acceptable to:

Replace the contacts or control

On a good single phase compressor, which winding terminals have the highest resistance?

Run to start

What is the term used to describe the output side of a transformer?

Secondary side

Excessive current can be caused by:

Short circuit

Which of the following materials would be best suited for use as a semi-conductor?

Silicon

A capacitor analyzer is designed to check:

The capacitance of the a capacitor

The rotation of a single phase motor is determined by:

The direction of current through the start winding

What is current flow?

The flow of electrons in a circuit

When resistors are wired parallel:

The voltage drop across each resistor will be the same as the applied source voltage

A three phase load requires a minimum of

Three supply lines

On an electronic oil safety switch, what changes the pressure signal to an electrical signal?

Transducer

To discharge a capacitor:

Use a 15,000 to 20,000 ohm, 2 to 5 watt resistor across the terminals

Transformers are rated by:

VA at the secondary

How are fuses sized?

Volts and amps

What is the correct formula for determining wattage?

W = E x I

The meter on a house measures the ____ passing through it.

Watts

Which of the following is the symbol for impedance in an AC circuit?

Z

Which of the following is the symbol for impedance?

Z

A step-up transformer increases

voltage