NOCTI Practice Exam 2

A simple DC circuit with a constant voltage, as resistance increases, current will:

• increase

• remain constant

• decrease

• spike

Answer explanation

The correct answer is:

✅ Decrease

Explanation:

According to Ohm’s Law, which states:

V=I×R

where:

• V = Voltage (constant in this case)

• I = Current

• R = Resistance

Rearranging for current (III):

I=V/R

Since voltage remains constant, if resistance increases, the denominator in the equation increases, causing current to decrease.

Why the other options are incorrect:

1. ❌ Increase – Current would increase only if resistance decreased (inverse relationship).

2. ❌ Remain Constant – Current depends on resistance, so it changes when resistance changes.

3. ❌ Spike – A spike implies a sudden surge, but increasing resistance causes a gradual reduction in current, not a spike.

Best Answer: As resistance increases, current decreases. ✅

When measuring current, the meter should be connected in:

• series parallel

• parallel

• reverse polarity

• series

Answer explanation

The correct answer is:

✅ Series

Explanation:

When measuring current (amperage), the meter (ammeter) must be connected in series with the circuit. This allows the entire current to flow through the meter, enabling an accurate reading.

Why the other options are incorrect:

1. ❌ Series Parallel – This term is not a valid connection type for measuring current.

2. ❌ Parallel – Voltmeters are connected in parallel, but an ammeter in parallel would cause a short circuit, potentially damaging the meter and the circuit.

3. ❌ Reverse Polarity – While reversing polarity may affect readings on certain meters, it does not define the correct connection method for measuring current.

Best Answer: To measure current, always connect the meter in series. ✅

Ohm's Law states:

• P = I x R²

• R = E / I

• E = I / R

• I = R / E

Answer explanation

The correct answer is:

✅ R = E / I

Explanation:

Ohm’s Law is a fundamental principle in electrical circuits and states:

V=I×RV = I \times RV=I×R

where:

• V (E) = Voltage (Electromotive Force, E is sometimes used instead of V)

• I = Current (in Amperes)

• R = Resistance (in Ohms)

Rearranging for R:

R=EIR = \frac{E}{I}R=IE​

Why the other options are incorrect:

1. ❌ P = I × R² squared – This is incorrect; the power equation is:

   P=V × I

   or

   P=I² × R

2. ❌ E = I / R – Incorrect; Ohm’s Law states

   E = I × R, not I divided by R.

3. ❌ I = R / E – Incorrect; solving for I gives:

   I=E / R​

Best Answer:

✅ R=EIR = \frac{E}{I}R=IE​ correctly represents Ohm’s Law.

4o

Circuit breakers are wired in ____ with a load.

• series

• parallel

• series/parallel

• opposition

Answer explanation

The correct answer is:

✅ Series

Explanation:

Circuit breakers are always wired in series with the load. This ensures that if there is an overcurrent or short circuit, the breaker will interrupt the entire current flow, protecting the circuit and connected devices.

Why the other options are incorrect:

1. ❌ Parallel – If a breaker were wired in parallel, current would continue flowing through the circuit even if the breaker trips, making it ineffective.

2. ❌ Series/Parallel – This is not a standard wiring configuration for circuit breakers.

3. ❌ Opposition – This is not a valid electrical wiring concept in this context.

Best Answer:

Circuit breakers are wired in series to effectively protect the circuit. ✅

The ____ is an electrical component that can hold a charge for a period of time.

• transformer

• capacitor

• inductor

• resistor

Answer explanation

The correct answer is:

✅ Capacitor

Explanation:

A capacitor is an electrical component that stores and holds an electric charge for a period of time. It consists of two conductive plates separated by an insulating material (dielectric). When voltage is applied, the capacitor stores energy in the form of an electric field and can release it when needed.

Why the other options are incorrect:

1. ❌ Transformer – A transformer transfers electrical energy between circuits using electromagnetic induction but does not store a charge.

2. ❌ Inductor – An inductor stores energy in a magnetic field (not as an electrical charge) when current flows through it.

3. ❌ Resistor – A resistor limits current flow and dissipates energy as heat but does not store charge.

Best Answer:

A capacitor holds a charge for a period of time. ✅

An electrical component referred to as a rheostat is a type of:

• variable resistor

• heater

• switch

• variable capacitor

Answer explanation

The correct answer is:

✅ Variable Resistor

Explanation:

A rheostat is a type of variable resistor used to control current flow in a circuit by adjusting resistance. It typically has two terminals and is commonly used in applications like dimming lights, motor speed control, and adjusting heater temperatures.

Why the other options are incorrect:

1. ❌ Heater – While a rheostat can control the power to a heater, it is not a heater itself.

2. ❌ Switch – A switch simply opens or closes a circuit, whereas a rheostat gradually adjusts resistance to control current.

3. ❌ Variable Capacitor – A capacitor stores and releases electrical energy, while a rheostat varies resistance, not capacitance.

Best Answer:

A rheostat is a type of variable resistor. ✅

Difference Between a Rheostat and a Potentiometer

Both rheostats and potentiometers are variable resistors, but they have different functions and circuit configurations.

FeatureRheostatPotentiometerFunctionControls current in a circuitControls voltage in a circuitNumber of Terminals2 terminals (input and output)3 terminals (input, output, and wiper)Wiring ConfigurationWired in series to vary resistance and currentWired in parallel or voltage divider mode to adjust voltageCommon UsesMotor speed control, light dimming, heater controlVolume control (audio devices), signal tuning, user-adjustable voltageAdjustment MechanismSliding or rotating contact changes resistance between two terminalsMiddle (wiper) terminal divides voltage across the resistor

Key Takeaway:

• A rheostat is used to control current by varying resistance in series.

• A potentiometer is used to control voltage by acting as a voltage divider.

The NEC standard color of ground wire is:

• red

• black

• white

• green

Answer explanation

The correct answer is:

✅ Green

Explanation:

According to the National Electrical Code (NEC), the standard color for ground wires is green or green with a yellow stripe. Ground wires provide a safe path for excess electricity to prevent electrical shocks and fires.

Why the other options are incorrect:

1. ❌ Red – Typically used as a secondary hot (live) wire in 240V circuits or three-phase systems.

2. ❌ Black – Usually represents the primary hot (live) wire in standard electrical wiring.

3. ❌ White – Designated for the neutral wire, which carries current back to the source.

Best Answer:

The NEC standard color for a ground wire is green or green/yellow. ✅

A bare wire is also used as a ground wire according to the National Electrical Code (NEC).

NEC Ground Wire Standards:

• ✅ Green or Green with Yellow Stripe → Insulated ground wire

• ✅ Bare Copper → Uninsulated ground wire (commonly used in residential wiring)

Why is a Bare Wire Used for Grounding?

• Cost-effective: No insulation needed, reducing material costs

• Efficient grounding: Direct connection to the ground

• Common in Romex (NM) cable: Found in residential wiring for outlets, lights, and appliances

So, both green and bare wires serve as ground wires in NEC-compliant electrical systems. ✅

When replacing a motor, special attention to information on the name plate is important because the nameplate specifies the ____ at which the motor may be operated.

• wattage

• resistance

• capacitance

• voltage

Answer explanation

The correct answer is:

✅ Voltage

Explanation:

When replacing a motor, the nameplate provides critical information, including the voltage rating, which specifies the correct operating voltage for the motor. Using an incorrect voltage can cause:

• Overheating and damage if the voltage is too high

• Insufficient power or failure to start if the voltage is too low

Why the other options are incorrect:

1. ❌ Wattage – The nameplate may list wattage (power), but voltage is the key factor that determines safe operation.

2. ❌ Resistance – Resistance is not a primary specification for motor operation; it’s more relevant for heating elements and resistors.

3. ❌ Capacitance – Capacitance is relevant for motors using capacitors (e.g., start or run capacitors), but it’s not the primary factor in motor operation.

Best Answer:

The nameplate specifies the voltage at which the motor may be operated. ✅

Using the chart, a 6-volt circuit that is 5-feet long and carries at least 12 amperes of current should use at least a ____ wire.

• 10-gauge

• 12-gauge

• 16-gauge

• 18-gauge

Answer explanation

Analyzing the Wire Gauge Selection Table to determine the correct wire gauge for a 6V circuit that is 5 feet long and carries at least 12 amperes of current, we see.

1. Locate 12A under the "Circuit Amperes" column.

2. Follow that row across to the 6V column.

3. Find the corresponding wire gauge for 5 feet.

From the table:

• 12A at 6V for 5 feet requires 18-gauge wire.

Answer:

✅ 18-gauge wire

An engineer has connected an oscilloscope to measure the output of a standard wall electrical outlet. The oscilloscope shows a 60 hertz sine wave measuring 120 volts. The signal is:

• analog

• digital

• non-continuous

• neutral

Answer explanation

The correct answer is:

✅ Analog

Explanation:

A standard wall electrical outlet in the U.S. provides AC (Alternating Current) power at 60 Hz and 120V RMS. The oscilloscope displays a sine wave, which is a continuous, smooth waveform—a key characteristic of analog signals.

Why the other options are incorrect:

1. ❌ Digital – Digital signals are discrete, typically represented as square waves (high/low, 1s and 0s). A sine wave is not digital.

2. ❌ Non-continuous – A sine wave is continuous by nature, meaning the signal flows smoothly without abrupt changes.

3. ❌ Neutral – "Neutral" refers to a wire in electrical wiring, not the type of signal.

Final Answer:

The 60 Hz sine wave from the outlet is an analog signal. ✅