circuits and controls

What is generally considered to be the maximum allowable (plus or minus) supply voltage variation?

5%

Three resistors are wired in series. Each has a value of 300 ohms. What is the total resistance of the circuit

900 ohms

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

A. 2300 watts

Voltage can be calculated by:

A. I times R

An ohmmeter should never be connected to:

A. a live circuit

A ______________________may be used on a single phase induction motor to disconnect the start windings after the motor starts

A. Centrifugal switch CorrectB. All of these C. Potential relayD. Amperage relay

A device used to control a motor is a;

A. contactor.B. line starter. CorrectC. all of theseD. relay.

Electricity can produce

A. heatB. lightC. magnetism CorrectD. all of the above

A device used to control a motor is a

A. relayB. contactorC. line starter CorrectD. all of the above

How are fuses sized?

Amps & Volts

A transformer has 1000 turns of wire in the primary coil and 2000 turns in the secondary coil. If 120 volts are applied, the output voltage will be;

B. 240 volts

Utility companies usually supply residential homes with _________service.

B. 240V, single phase, three wire

A transformer has 1000 turns of wire in the primary coil and 500 turns in the secondary coil. If 120 volts are applied, the output voltage will be;

B. 60 volts

Contactors are rated according to the maximum amperage through the;

B. contacts

Contactors are rated according to the maximun amperage through the;

B. contacts

A step up transformer increases;

B. voltage

Capacitors are rated in;

B. microfaradsC. volts

Overcurrent can be caused by

B. overloadC. short circuitsD. ground faults

Direction of rotation of a single phase induction motor is determined by;

CorrectA. the direction of current flow through the start winding

What would be the result of three defrost heaters, each 12.5 ohms, wired in series to a 115 volt power supply, if the heaters were to supply a 360 watt heating load?

Heaters operate normally

When testing the windings of a single phase motor, Technician #1 says that the common and run terminals show the lowest resistance. technician #2 says that the pair of terminals with the highest resistance will indicate that the other terminal is the common. Who is correct?

both

Impedance in a circuit is the result of;

capacitive reactance.

To change direction of rotation of a three phase motor

change the position of any two supply wires.

A solenoid valve operates on the principle of

electromagnetism

When testing a motor with an ohmmeter, one winding show a 1000 ohm continuity to the motor frame. This is an indication of a good safety ground

false

Fuses are used to protect;

loads

when current flows, a_______________is produced around the conductor.

magnetic field

The thermal overload contacts on a line starter are usually __________reset.

manual

The ____________drawing illustrates where the components are located on the appliance..

pictorial

Like charges will

repel each other

The terminals T1,T2, & T3 are located at the ______ of a contactor.

top

How many switches can be connected to a contactor coil control circuit?

unlimited

How may switches can be connected to a contactor coil control circuit

unlimited

If contacts become dirty or pitted, it is acceptable to sand or file them as a permanent repair.

. False

What is resistance?

. Opposition to current flow

A capacitor opposes current flow in a circuit. This opposition is called;

. capacitive reactance

When testing a capacitor with an analog ohmmeter, the needle on the meter should;

. deflect towards zero then return to infinite reading

What is impedence?

Opposition to alternating current flow.

What is current flow?

The flow of electrons in the circuit

Transformers are rated according to;

VA at the secondary

Any material that will readily release electrons is called

a conductor

Capacitors are always connected ____________ to the start windings?

in series

An electron has

negative charge

Two 120 volt motors are wired in series, one is a 60 watt motor, the other is a 4 watt motor. The result would be;

neither motor would operate normally

What meter is used to bench check a motor for shorts or open windings?

ohmmeter