Maryland Journeyperson Electrician

An ammeter is connected in series to carry the full circuit current and must have very low internal resistance, while a voltmeter is connected in parallel across a component to read potential difference and has very high internal resistance so it draws negligible current.

Type MC with interlocked-type armor or corrugated sheath requires a minimum bend radius of seven times the external diameter of the metallic sheath, while Type MI greater than 19 mm (3/4 in.) but not more than 25 mm (1 in.) in external diameter requires ten times the external diameter.

EMT must be secured at intervals not exceeding 3 m (10 ft) and within 900 mm (3 ft) of each termination, while Type MC cable, unless otherwise provided, must be secured at intervals not exceeding 1.8 m (6 ft).

EMT must be securely fastened within 900 mm (3 ft) of each outlet box, junction box, device box, cabinet, conduit body, or other tubing termination, while FMC must be securely fastened within 300 mm (12 in.) of each box, cabinet, conduit body, or other conduit termination.

Real power is the actual power consumed (P = √3 × V × I × cos θ in three phase), while apparent power is the vector sum of real and reactive power found by S = P ÷ PF and it stays unchanged when power factor changes at constant voltage and current.

Inductive reactance uses inductance L with frequency f (XL = 2πfL); substituting capacitance C makes the formula wrong.

A metal underground water pipe qualifies as a grounding electrode with 10 ft or more in direct earth contact, while a concrete-encased electrode requires at least 20 ft of bare or zinc galvanized steel rebar not less than 1/2 in. diameter or bare copper not smaller than 4 AWG, encased in at least 2 in. of concrete.

The earth shall not be considered an effective ground-fault current path; an effective path must be a low-impedance circuit capable of safely carrying maximum ground-fault current and facilitating operation of the overcurrent device.

Even with 90°C-rated conductors, for circuits over 100 amperes (or marked for conductors larger than 1 AWG) the ampacity must be determined at 75°C unless the equipment is listed and identified for use at a higher rating.

Type MC cable without an overall nonmetallic covering (and Type MI without a nonmetallic covering) is permitted in other spaces used for environmental air, while Type NM, ENT, and PVC are not permitted unless enclosed in an approved metal raceway.

A terminal for the grounded conductor on receptacles, plugs, and connectors is identified by metal or metal coating substantially white or silver, or the word 'white' or letter 'W'; a main or system bonding jumper that is a screw only must be identified with a green finish visible with the screw installed.

For circuits over 250 volts to ground, continuity of metal raceways and cables with metal sheaths must use one of the service methods of 250.92(B) except bonding to the grounded service conductor, because that method applies only to service equipment.

A voltmeter across a good fuse reads about 0 V because a good fuse drops almost no voltage, whereas a 120 V reading across the fuse indicates the fuse itself is open.