1.
A non-metallic material that allows the flow of electrons is a
Correct Answer
A. Semi-conductor
Explanation
A semi-conductor is a non-metallic material that allows the flow of electrons. Unlike conductors, which have high conductivity, and insulators, which have low conductivity, semi-conductors have moderate conductivity. This means that they can conduct electricity under certain conditions, such as when exposed to heat or light. Semi-conductors are widely used in electronic devices, such as transistors and diodes, due to their ability to control the flow of electrons and their versatility in conducting or blocking electrical current.
2.
The amount of voltage drop across a short circuit:
Correct Answer
D. Is always 0V
Explanation
The correct answer is "is always 0V". In a short circuit, the resistance is extremely low or zero, causing a large current to flow. According to Ohm's Law (V = IR), if the resistance is zero, the voltage drop across it will also be zero. Therefore, in a short circuit, the voltage drop is always 0V.
3.
In a parallel circuit, the voltage across each branch:
Correct Answer
A. Is always equal to the source voltage
Explanation
In a parallel circuit, the voltage across each branch is always equal to the source voltage. This is because in a parallel circuit, the voltage across each branch is the same as the voltage across the source. This is because the voltage is divided equally among the branches, and the total voltage across the branches adds up to the source voltage. Therefore, the voltage across each branch in a parallel circuit is always equal to the source voltage.
4.
The amount of electricity going past a given point in a circuit is called.
Correct Answer
B. Current
Explanation
The amount of electricity flowing through a given point in a circuit is referred to as current. Current is measured in amperes and represents the rate of flow of electric charge. It is a fundamental concept in electrical engineering and is essential for understanding the behavior of circuits and devices. Voltage, resistance, and inductance are related concepts but represent different aspects of electrical circuits.
5.
What is the maximum VA output of a class I transformer?
Correct Answer
D. 1000 VA
Explanation
The maximum VA output of a class I transformer is 1000 VA. VA stands for Volt-Ampere, which measures the apparent power of an electrical circuit or device. In this case, the transformer is capable of delivering a maximum apparent power of 1000 VA.
6.
A 1000 ohm resistor with 5 volts across it has how much current flowing through it?
Correct Answer
C. 5.0 mA
Explanation
The current flowing through a resistor can be calculated using Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the voltage across the resistor is 5 volts and the resistance is 1000 ohms. By substituting these values into the formula, we can calculate the current as 5.0 mA (milliamperes).
7.
Four 100 ohm resistors connected in parallel have the equivalent value of
Correct Answer
D. 25.0 ohm
Explanation
When resistors are connected in parallel, the equivalent resistance is calculated using the formula 1/Req = 1/R1 + 1/R2 + 1/R3 + 1/R4. In this case, since all four resistors have the same value of 100 ohms, the equation becomes 1/Req = 1/100 + 1/100 + 1/100 + 1/100. Simplifying this equation gives 1/Req = 4/100. Taking the reciprocal of both sides gives Req = 100/4, which simplifies to 25.0 ohm. Therefore, the equivalent value of four 100 ohm resistors connected in parallel is 25.0 ohm.
8.
A resistor R1 is connected to a power supply. If another resistor R2 is connected in parallel to the same power supply, how much current will flow out of the power supply, as compared to the first circuit, if 2XR1 = R2?
Correct Answer
C. 1.5X as much as the 1st circuit
Explanation
When a resistor R2 is connected in parallel to the power supply, the total resistance of the circuit decreases. According to Ohm's Law (V = IR), as the resistance decreases, the current flowing through the circuit increases. In this case, since 2XR1 = R2, the total resistance of the circuit is reduced by half. Therefore, the current flowing out of the power supply will be 1.5 times as much as the first circuit.
9.
The equation for Watt's Law is
Correct Answer
D. All of the above
Explanation
The correct answer is "all of the above" because all three equations mentioned (P=I2r, P=I x E, P=(E)(E) /R) are valid representations of Watt's Law. Watt's Law states that power (P) is equal to the product of current (I) and voltage (E), or power is equal to the square of current multiplied by resistance (R). Therefore, all three equations are correct and can be used to calculate power in different scenarios.
10.
Electrical current is measured using
Correct Answer
B. An ammeter
Explanation
An ammeter is used to measure electrical current. It is specifically designed to measure the flow of electric current in a circuit. Unlike an ohmmeter, which measures resistance, a voltmeter, which measures voltage, or an oscilloscope, which measures the waveform of an electrical signal, an ammeter is the appropriate tool for directly measuring the amount of current flowing through a circuit.
11.
When checking the polarity of a phone line, the positive test lead of the meter should be connected to
Correct Answer
C. Tip
Explanation
When checking the polarity of a phone line, the positive test lead of the meter should be connected to the "tip" of the phone line. The tip is the positive terminal of the phone line, and connecting the positive test lead to it allows for accurate measurement of the voltage or polarity.
12.
The source voltage is divided among resistors in a circuit.
Correct Answer
B. If they are in series
Explanation
When resistors are connected in series, the total resistance is equal to the sum of individual resistances. According to Ohm's law, V = IR, where V is the voltage, I is the current, and R is the resistance. In a series circuit, the same current flows through each resistor. Therefore, the voltage is divided among the resistors based on their individual resistance values. The resistor with higher resistance will have a larger voltage drop, while the resistor with lower resistance will have a smaller voltage drop. Hence, the correct answer is "if they are in series."
13.
Voltage measured across an open switch is
Correct Answer
C. The same as the source voltage
Explanation
When a switch is open, it does not allow any current to flow through it. Therefore, there is no voltage drop across the switch. The voltage measured across an open switch is the same as the source voltage because there is no load to cause any voltage drop. So, the correct answer is "the same as the source voltage."
14.
What is the total current draw, in amps, of 8 motion detectors if each device consumes 26 mA?
Correct Answer
B. .208 A
Explanation
The total current draw of the 8 motion detectors can be calculated by multiplying the current consumed by each device (26 mA) by the number of devices (8). This gives us a total current draw of 208 mA. To convert this to amps, we divide by 1000, resulting in 0.208 A. Therefore, the correct answer is 0.208 A.
15.
The insulating material in a capacitor is called the
Correct Answer
D. Dielectric
Explanation
A dielectric is the insulating material used in a capacitor. It is a non-conductive substance that is placed between the two conductive plates of a capacitor to separate them and prevent electrical current from flowing directly between them. The dielectric material increases the capacitance of the capacitor by storing electrical energy in its electric field. Fiberglass, resistor, and semi-conductor are not typically used as dielectric materials in capacitors.
16.
Two identical voltmeters are placed in series across a 12V DC supply. Each meter reads
Correct Answer
B. 6V DC
Explanation
When two identical voltmeters are placed in series across a 12V DC supply, the total voltage across both meters is divided equally. Therefore, each meter will read half of the total voltage, which is 6V DC.
17.
Photoelectric beams must be installed as close as possible to the fence being protected maximum protection.
Correct Answer
B. False
Explanation
The statement is false because photoelectric beams should be installed at a distance from the fence being protected to ensure maximum protection. Placing the beams too close to the fence may result in false alarms or the beams being easily bypassed by intruders. Therefore, it is important to have an adequate distance between the beams and the fence for effective security.
18.
A standard surface mount magnetic reed contact mounted on a commercial aluminum front entry door frame can operate a 14V-225mA doorbell.
Correct Answer
B. False
Explanation
A standard surface mount magnetic reed contact is typically used for sensing purposes, such as detecting when a door or window is opened or closed. It is not designed to directly operate a doorbell, which typically requires a power source and a chime or buzzer mechanism to produce sound. Therefore, the statement is false.
19.
A single diode can be used to change the direction of the current flow.
Correct Answer
B. False
Explanation
A single diode cannot change the direction of current flow. A diode is a semiconductor device that allows current to flow in one direction and blocks it in the opposite direction. It acts as a one-way valve for current. Therefore, a diode can only allow current to flow in one direction, but it cannot change the direction of current flow. Hence, the statement is false.
20.
In DC circuits, capacitors are used mainly to
Correct Answer
B. Filter fluctuation voltage levels
Explanation
Capacitors are commonly used in DC circuits to filter fluctuation voltage levels. This is because capacitors have the ability to store and release electrical energy quickly, which helps to smooth out any sudden changes or fluctuations in voltage. By placing a capacitor in parallel with a load, it can absorb any spikes or dips in voltage, providing a more stable and consistent power supply. This is particularly useful in sensitive electronic devices that require a steady voltage to function properly.
21.
The device which operates on the principle of mutual inductance of parallel coils is
Correct Answer
B. Transformer
Explanation
A transformer operates on the principle of mutual inductance of parallel coils. It consists of two or more coils wound around a common magnetic core. When an alternating current flows through the primary coil, it creates a changing magnetic field which induces a voltage in the secondary coil. This allows for the transfer of electrical energy from one circuit to another without direct electrical connection. Transformers are commonly used in power transmission and distribution systems to increase or decrease voltage levels.
22.
In AC circuits, the unit Hz refers to
Correct Answer
C. Frequency of a signal
Explanation
The unit Hz refers to the frequency of a signal in AC circuits. Hz stands for Hertz, which is the unit of measurement for frequency. Frequency represents the number of cycles or oscillations that occur in one second. In AC circuits, the frequency of the signal determines the rate at which the current alternates direction. It is an important parameter in AC circuits as it affects various aspects such as the behavior of capacitors and inductors, the efficiency of power transmission, and the performance of electrical devices.
23.
When installing a magnetic door sensor as part of a security system, where should the sensor and its magnet be placed?
Correct Answer
A. The sensor should be installed on the door frame, and the magnet on the moving part of the door.
Explanation
In a typical installation of a magnetic door sensor, the sensor itself is mounted on the door frame, stationary, while the magnet is attached to the door, the part that moves. This setup ensures that when the door is closed, the magnet comes close to the sensor, closing the circuit and signaling that the door is securely closed. When the door opens, the magnet moves away, breaking the circuit and triggering the alarm if the system is armed. This method reliably monitors the opening and closing of doors.
24.
When correctly measuring a standard alarm power supply voltage your digital VOM reads +6.80 VDC. No devices are connected to the terminals. This means that
Correct Answer
C. The voltage is to low for the system devices to function correctly
Explanation
When the digital VOM reads a voltage of +6.80 VDC, it indicates that the voltage is too low for the system devices to function correctly. This means that the power supply is not providing enough voltage for the devices to operate properly.
25.
A diode is a device which
Correct Answer
B. Allows current to flow in one direction
Explanation
A diode is a device that allows current to flow in one direction. This is because it is designed with a p-n junction, which acts as a one-way gate for electrical current. When the diode is forward-biased, meaning the positive voltage is applied to the p-side and the negative voltage to the n-side, it allows current to flow freely. However, when the diode is reverse-biased, it acts as an insulator and prevents current flow. Therefore, the correct answer is that a diode allows current to flow in one direction.
26.
Electrostatic discharge can damage most modern electronic circuits
Correct Answer
A. True
Explanation
Electrostatic discharge (ESD) refers to the sudden flow of electricity between two objects with different electric potentials. This discharge can cause damage to electronic circuits by exceeding their voltage tolerance levels. Most modern electronic circuits are designed to be sensitive and can be easily damaged by ESD. Therefore, it is true that electrostatic discharge can damage most modern electronic circuits.
27.
Where should an alarm installer keep her licence
Correct Answer
D. None of the above
Explanation
An alarm installer should keep her license on her person at all times while working. Keeping it in the truck glove box, her briefcase, or a safety deposit box would not be appropriate as it may not be easily accessible when needed for verification or inspection.
28.
A 4.5 amp-hour battery will provide 300 mA of current for
Correct Answer
D. 15 hours
Explanation
A 4.5 amp-hour battery can provide 300 mA of current for 15 hours. This is because the capacity of the battery is given in amp-hours, which means it can deliver a certain amount of current (in this case, 4.5 amps) for a specific duration (15 hours). Since the load is not specified in the question, we can assume that the battery will provide 300 mA of current for the full 15 hours.
29.
The input coil of a transformer is called the
Correct Answer
A. Primary
Explanation
The input coil of a transformer is called the primary coil because it is the coil that receives the input voltage. It is connected to the power source and is responsible for transferring the electrical energy to the secondary coil. The primary coil typically has a higher number of turns than the secondary coil, which allows for voltage transformation in the transformer.
30.
Which of the following is not true
Correct Answer
A. Insulation thickness determines the current capacity of a wire
Explanation
The correct answer is "insulation thickness determines the current capacity of a wire." This statement is not true because insulation thickness does not determine the current capacity of a wire. The current capacity of a wire is determined by its cross-sectional area and the material it is made of. Thicker insulation may provide better protection against external factors, but it does not directly affect the wire's ability to carry current.
31.
Disconnected from the control, an N/C alarm circuit with a correctly installed 5.6K end of line resistor and a open device on the loop will show a total circuit resistance of
Correct Answer
C. Open circuit
Explanation
When the N/C alarm circuit is disconnected from the control and there is an open device on the loop, it means that the circuit is not complete and there is a break in the circuit. In an open circuit, there is no continuous path for the electric current to flow, resulting in infinite resistance. Therefore, the total circuit resistance in this scenario would be an open circuit.
32.
A 100 Watt 120 Volt CCTV power supply consumes how many amps?
Correct Answer
C. 0.83 amps
Explanation
The correct answer is 0.83 amps. To calculate the amperage, we can use the formula P (power in watts) = V (voltage in volts) x I (current in amps). Rearranging the formula, we can find that I = P / V. Plugging in the values, we get I = 100W / 120V = 0.83 amps. Therefore, a 100 Watt 120 Volt CCTV power supply consumes 0.83 amps.
33.
Voltage drop across a device is calculated by
Correct Answer
A. Multiplying the current through it by its resistance
Explanation
The voltage drop across a device is calculated by multiplying the current through it by its resistance. This is determined by Ohm's Law, which states that the voltage drop (V) is equal to the current (I) multiplied by the resistance (R), V = I * R. Therefore, to find the voltage drop, we need to know the current flowing through the device and the resistance of the device.
34.
In a parallel circuit, the currents in the individual branches flow equally only if
Correct Answer
D. All V/R values are identical in the branches
Explanation
In a parallel circuit, the currents in the individual branches flow equally only if all V/R values are identical in the branches. This means that the voltage-to-resistance ratio (V/R) must be the same in each branch. If the V/R values are different, the currents in the branches will also be different, resulting in an unequal distribution of current. Therefore, for equal currents to flow in each branch, the V/R values must be identical.
35.
Surge protectors should be considered only after a system has been damaged once by a power surge, since it will likely happen again?
Correct Answer
B. False
Explanation
The statement suggests that surge protectors should only be considered after a system has been damaged once by a power surge, implying that it is necessary to experience damage before taking preventive measures. However, this is incorrect. Surge protectors are designed to prevent damage from power surges, and it is recommended to use them as a proactive measure to protect electronic devices and systems from potential damage caused by power surges. Therefore, the correct answer is False.
36.
When measuring the continuity of an alarm circuit, the circuit should be
Correct Answer
C. Disconnected from the alarm panel
Explanation
When measuring the continuity of an alarm circuit, it is important to disconnect it from the alarm panel. This is because measuring continuity requires breaking the circuit to check if there is a continuous path for the current to flow. If the circuit is still connected to the alarm panel, it may interfere with the measurement and give inaccurate results. Therefore, disconnecting the circuit from the alarm panel ensures that the measurement is accurate and reliable.
37.
A step down transformer
Correct Answer
C. Provides a reduced AC voltage
Explanation
A step down transformer is designed to lower the voltage of an alternating current (AC) power source. It has more turns on its secondary coil than on its primary coil, which results in a reduced voltage output. This allows the transformer to provide a lower AC voltage to devices or systems that require it. Therefore, the correct answer is "provides a reduced AC voltage."
38.
The best metal to use as a core for a magnetic door lock is
Correct Answer
C. Soft iron
Explanation
Soft iron is the best metal to use as a core for a magnetic door lock because it has high magnetic permeability. This means that it can easily conduct and concentrate magnetic flux, making it ideal for creating a strong magnetic field. Soft iron also has low coercivity, meaning it can be easily magnetized and demagnetized. Additionally, soft iron is relatively inexpensive and readily available, making it a practical choice for magnetic door locks.
39.
The names of the contact on a SPDT relay are
Correct Answer
C. Common, NC, NO
Explanation
The correct answer is "common, NC, NO". In a SPDT (Single Pole Double Throw) relay, there are three terminals: common (C), normally closed (NC), and normally open (NO). The common terminal is the central terminal that is connected to either the NC or NO terminal depending on the relay's state. The normally closed terminal is connected to the common terminal when the relay is not energized, and it opens when the relay is energized. On the other hand, the normally open terminal is not connected to the common terminal when the relay is not energized, and it closes when the relay is energized.
40.
The data "bits" on the magnetic stripe of a access card can be copied by anyone with a card printer
Correct Answer
A. True
Explanation
The given statement is true because the data stored on the magnetic stripe of an access card can indeed be copied by anyone with a card printer. Magnetic stripe cards use a simple encoding system that can be easily replicated, making them vulnerable to unauthorized duplication. This is why additional security measures, such as encryption or the use of more advanced technologies like smart cards, are often implemented to prevent unauthorized access or fraud.
41.
Which of the following is true?
Correct Answer
B. A magnetic field exists around any current-carrying conductor
Explanation
A magnetic field exists around any current-carrying conductor. When an electric current flows through a conductor, it creates a magnetic field around it. This is a fundamental principle of electromagnetism known as Ampere's law. The strength and direction of the magnetic field depend on the magnitude and direction of the current. This principle is widely used in various applications, such as electric motors, transformers, and magnetic resonance imaging (MRI) machines.
42.
In an electric door strike, the term "fail secure" means
Correct Answer
B. The door locks when power is removed
Explanation
In an electric door strike, the term "fail secure" means that the door locks when power is removed. This means that even in the event of a power failure or interruption, the door will remain locked and secure. This is important for security purposes, as it ensures that unauthorized individuals cannot gain access to the door when there is no power.
43.
The primary goal of a security system is
Correct Answer
B. Reduce the customer's property loss
Explanation
The primary goal of a security system is to reduce the customer's property loss. This means that the system is designed to prevent or minimize any damage or theft that may occur on the customer's property. While making a loud noise, calling the neighbors and police, and scaring the burglar may be secondary effects of a security system, the main purpose is to protect the customer's belongings and assets.
44.
According to workers compensation, anyone can work on an energized circuit
Correct Answer
B. False
Explanation
According to workers compensation regulations, working on an energized circuit is highly dangerous and should only be done by qualified and trained individuals. Therefore, the statement that anyone can work on an energized circuit is false.
45.
The minimum allowable distance between parallel runs of low-voltage alarm wire and high voltage wire is
Correct Answer
A. 50 cm
Explanation
The correct answer is 50 cm. This distance is necessary to prevent interference or potential damage to the low-voltage alarm wire caused by the high voltage wire. Keeping a minimum distance of 50 cm ensures that there is enough separation between the two wires to maintain safety and proper functioning of the alarm system.
46.
What is the minimum burial depth allowable for a communication cable in a vehicular area?
Correct Answer
C. 900 mm
Explanation
The minimum burial depth allowable for a communication cable in a vehicular area is 900 mm. This depth is necessary to ensure the cable is adequately protected from potential damage caused by vehicular traffic. A deeper burial depth provides a greater level of protection and helps to prevent accidental damage to the cable, ensuring reliable communication infrastructure.
47.
What is the maximum number of bends allowed in a run of conduit?
Correct Answer
A. Any combination of bends to a total of 360 degrees
Explanation
The correct answer is any combination of bends to a total of 360 degrees. This means that you can have multiple bends in a run of conduit as long as the total angle of all the bends combined does not exceed 360 degrees. This allows for flexibility in the installation process while still ensuring that the conduit remains within acceptable limits.
48.
Which of the following best describes the rule for running wire in a return-air plenum ceiling?
Correct Answer
B. All conductors must be either in conduit or rated for installation in plenum ceilings
Explanation
The correct answer is "all conductors must be either in conduit or rated for installation in plenum ceilings." This means that when running wire in a return-air plenum ceiling, the conductors must be either enclosed in conduit or specifically designed and rated for installation in plenum ceilings. This is to ensure safety and compliance with regulations, as plenum ceilings are spaces that can potentially contain air circulation systems and can pose fire hazards if not properly wired.
49.
True or false, on a two storey wood frame building it is required to cap or plug unused conduit that would allow the passage of fire or smoke between the first and second floor?
Correct Answer
A. True
Explanation
On a two storey wood frame building, it is necessary to cap or plug unused conduit that would allow the passage of fire or smoke between the first and second floor. This is important for fire safety measures as it helps prevent the spread of fire and smoke between the floors, reducing the potential damage and danger to occupants. Capping or plugging the unused conduit ensures that there are no open pathways for fire or smoke to travel through, maintaining the integrity of the building's fire protection system.
50.
Is it permissible to run access control wiring in an elevator shaft?
Correct Answer
B. No
Explanation
It is not permissible to run access control wiring in an elevator shaft.