ac/dc saca study guide

How many degrees apart are the phases of a balanced three phase system?

120

What does an electrical schematic not show?

Physical connections

Resistance is measured in units of?

Ohms

What is the power formula?

P=IxE

What is power measured in?

Watts

What is the function of an inductor?

It opposes a change in current flow

A coil is a_________?

Output

Which of the following is an output?

Solenoid

What is the formula to solve for current?

I=E/R

When troubleshooting a circuit, what can be said if the total resistance of the parallel circuit does not change when a branch is removed?

An open exists in the removed branch

The unit for electromotive force (emf) is?

Volt

What is the relationship of the applied voltage across two electrical components in parallel with each other?

They are the same

Which feature of a ground circuit creates a safe path for current?

Low resistance to earth

An ohmmeter is reading total circuit resistance reads 0 ohms when all branches are connected and reads 200 ohms when a branch is disconnected. What condition exists?

There is a short in the disconnected branch

A series circuit has a total of three resistors, 5 ohms, 3 ohms, and 16 ohms. What is the Rt of this circuit?

24 ohms

When testing an indicator light, one must first remove it from the circuit and place a multimeter across its threaded area and base or input leads. What is the next step in testing the indicator light?

Set the meter for resistance and check the reading

What is the secondary coil voltage of a transformer that has 120v supplied, 400 turns on the primary and 100 turns on the secondary?

30v

A voltmeter is connected in a circuit by?

Placing the test leads in parallel with the circuit device

To measure current in a current, how is the meter placed in the circuit?

In series with the circuit or component

Which of the following is the formula for TR

TR=NP/NS

Which of the following is an immediate danger of unsecured electrical cords?

Trip hazard

A series circuit has three resistors. The voltage measured across each resistor is 4vdc, 8vdc, and 12vdc. What is the Et of this circuit?

24

When checking for voltage in a circuit, the test leads of the multimeter must be placed in______with the circuit?

Parallel

How many seconds will it take in a RC circuit to completely charge if the RC has a time constant of .06 seconds?

0.3

If Parallel paths are not disconnected, an ohmmeter placed across parallel paths will read?

Lower in all circuits

A circuit contains three equal value resistors in series. What will a technician do to calculate the total resistance?

Add the values together

A fatal current can be as small as:

0.1A

When testing a manual switch that is isolated/out of circuit, the multimeter leads are placed across the switch input leads. While operating the switch, what is the next step?

Check for a resistance change

In a parallel circuit, total current is equal to?

The sum of the individual branch circuit current

How are transformers sized?

Volt amps

Which of the following is an input

NOPB

A series circuit has three resistors in the circuit and another resistor is added for a total of four resistors. What happens to the current in the circuit?

Current remains the same

Which of the following is the wire size that will handle the highest current?

awg8

What are the procedures for testing current with a clamp-on ammeter?

Set the meter to amperage and place the clamp around a single conductor

What is the symbol for current?

I

What is the measure of a components ability to resist the flow of current in a circuit?

Resistance

A motor is a type of ?

Load

A series circuit flows in_______direction?

One

Which of the following is true about a fuse?

A fuse can only be used one time

What is defined as the flow of electrons in a conductor

Electricity

What it the symbol for volts?

V

N.O is short for?

Normally Open

N.C. is short for?

Normally Closed

A common source of DC voltage is what?

A battery

When checking for anchorage, what do you need to do?

Keep power on and place the test leads in series with the circuit

What are the two main components of a control relay?

Switch and coil

A switch is tested in a circuit and is reading 120 watts. What do we know about the switch?

Switch is open

Which of the following is correct when measuring for resistance of a component in a circuit?

Turn the power off, disconnect one end of the component, set the meter to resistance.

A voltmeter is reading voltage across a normally closed push button. What does this tell us about the state of the contacts on the switch?

They are open

What change occurs in a circuit powered by a battery when a parallel branch is added?

Resistance decreases

Two normally open switches wired in parallel with each other is an example of what type of logic?

OR

What is the state of a capacitor if its resistance is continuously close to zero?

Its shorted

T/F: In order to take a voltage reading, the test leads must be placed in series.

False

Rotary motion is the output of which electrical output device?

Motor

LOTO is a safe work practice that is not designed to protect the worker from?

Contacting process materials