A 12-volt DC alarm circuit has a total resistance of 48 ohms. What is the circuit current?
General Electrical Knowledge
Question · Easy
14 on 15, 12 on 20, 10 on 30
Short
An outdoor siren draws 1.5 amperes from a 12-volt DC auxiliary output. What power does the siren consume?
Three resistors of 10 ohms, 15 ohms, and 25 ohms are connected in series. What is the total resistance?
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Two 24-ohm resistors are connected in parallel. What is the equivalent resistance?
Question · Medium
A 4-ohm speaker is driven at 2 amperes. What power is dissipated in the speaker?
NEC 210.19 Informational Note No. 4 recommends limiting voltage drop on a branch circuit to no more than which amount under load?
Per 2020 NEC Table 310.16, what is the allowable ampacity of 12 AWG copper THWN in a raceway at 75°C, not more than three current-carrying conductors, 30°C ambient?
Unless an exception in 240.4(E) or (G) applies, what is the maximum overcurrent device rating permitted to protect a 12 AWG copper conductor?
A 12-volt DC power run is 80 feet one-way to a 0.40-ampere load. Using copper K = 12.9 and 22 AWG (640 circular mils), what is the approximate voltage drop?
Question · Hard
A 0.50-ampere current flows through a 16-ohm resistor. What voltage appears across the resistor?
According to 2020 NEC Table 250.122, what is the minimum copper equipment grounding conductor size for a 20-ampere branch circuit?
A single rod, pipe, or plate grounding electrode is installed. Under NEC 250.53(A)(2), a supplemental electrode is not required if that single electrode has a resistance to earth of not more than which value?
A metal device box contains two 14-2 with ground NM cables, one internal cable clamp, and one single-pole switch. Using NEC 314.16, what minimum box volume is required?
NEC 300.14 requires at least how much free conductor in each box for splices or connections, measured from each cable or raceway entrance?
For equipment operating at 150 volts to ground or less, what is the minimum depth of working space in front of the equipment under NEC Table 110.26(A)(1) Condition 1?
Which of the following is a standard ampere rating for fuses and inverse-time circuit breakers listed in NEC 240.6(A)?
A 120/240-volt service has 2 AWG copper ungrounded conductors. Per Table 250.66, what is the minimum copper grounding electrode conductor size?
In a series circuit, which quantity is the same through every component?
Where a cable or raceway is installed through bored holes in wood framing members, NEC 300.4(A)(1) requires the edge of the hole to be at least how far from the nearest edge of the wood member unless a steel plate is used?
Six current-carrying 12 AWG THHN copper conductors are installed in one raceway in a 30°C ambient. After the NEC 310.15(C)(1) adjustment, what is the adjusted ampacity of each conductor?
For box-fill calculations under NEC 314.16(B)(4), a single-yoke duplex receptacle counts as how many conductor volume allowances?
Unless the equipment is listed and marked otherwise, NEC 110.14(C)(1) generally requires conductors 14 AWG through 1 AWG to be selected from which temperature column for termination provisions on circuits rated 100 amperes or less?
A 12-volt DC run is 60 feet one-way and carries 1.2 amperes. Using copper K = 12.9, what is the smallest standard copper conductor that keeps voltage drop from exceeding 0.60 volt (5 percent)?
In a parallel circuit, which quantity is the same across every branch?
Per 2020 NEC Table 300.5, what is the minimum cover for a direct-burial cable, 0 to 1000 volts, in a location not otherwise specified (Column 1, row 1)?
Two 24-ohm resistors in parallel are connected in series with an 8-ohm resistor across a 12-volt source. What is the total circuit current?
NEC 250.94 requires an intersystem bonding termination to be provided for connecting bonding conductors of limited-energy systems. Where must that termination be located?
A 10 AWG copper THWN conductor is installed in a raceway at 75°C with not more than three current-carrying conductors. Which statement is correct under the 2020 NEC?
NEC Article 725 classifies remote-control, signaling, and power-limited circuits into which groups?
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Why does the NEC allow simplified wiring methods for Class 2 circuits compared with Class 1 or power circuits?
A power-limited Class 1 circuit is limited to which maximum voltage and power?
Which 2020 NEC article covers communications circuits, including outside wiring for burglar-alarm circuits that extend from the communications utility to the premises communications equipment?
Unless an exception in 725.136 is met, Class 2 and Class 3 circuit conductors must be separated by at least how much from electric light, power, and Class 1 conductors?
Which cable type is specifically listed for Class 2 use in other-space-used-for-environmental-air (plenum) applications?
NEC 800.100 generally requires the communications grounding conductor or bonding conductor to be copper or other corrosion-resistant material and not smaller than which size?
Most listed Class 2 alarm-panel transformers are limited to a nameplate output of about which power?
In one- and two-family dwellings, NEC 800.100(A)(4) generally limits the communications grounding conductor length to not more than which distance, unless a separate electrode is installed?
If a separate grounding electrode is installed for a communications system, NEC 800.100(D) requires that electrode to be bonded to the power grounding electrode system with a copper or equivalent conductor not smaller than which size?
May Class 2 burglar-alarm conductors be installed in the same raceway with 120-volt lighting conductors if no barrier is provided?
Which of the following substitutions is permitted where a Class 2 plenum cable is required?
How does a Class 3 circuit differ from a Class 2 circuit in the NEC safety model?
What is the minimum conductor size generally permitted for a Class 1 circuit, and what insulation voltage rating is required?
A South Carolina burglar-alarm contractor is wiring a premises intrusion system with Class 2 initiating circuits. Which NEC article governs those initiating circuits?
NEC 725.24 requires Class 2 and Class 3 circuits to be installed in a neat and workmanlike manner. Which practice complies?
In an other space used for environmental air (a plenum ceiling used as a return-air path), which installation is acceptable for burglar-alarm cable?
Where are the voltage, current, and VA limitations for Class 2 and Class 3 power sources tabulated in the 2020 NEC?
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