TL;DR
Fractions and Decimals: Numerical representations of parts of a whole essential for measurement and calculation in the trades.
Fractions and Decimals
Definition
Numerical representations of parts of a whole essential for measurement and calculation in the trades.
Step-by-Step Procedure
Numerical representations of parts of a whole essential for measurement and calculation in the trades. Tested on the IBEW aptitude exam. Electricians use these daily for conduit measurements and load calculations.
Relevant formula: Conduit fill is 1 wire=53%, 2 wires=31%, 3+ wires=40% of conduit area. Variables: Wire area from Chapter 9 Table 5, conduit area from Table 4.
Equipment & Tools
Tools and equipment for fractions and decimals include multimeters (for voltage, current, and resistance measurement), clamp meters (for non-contact current measurement), megohmmeter (for insulation resistance testing), and conduit benders (for EMT and rigid conduit). All test equipment must be rated for the voltage being measured. A Category III meter minimum for distribution-level work, Category IV for service entrance.
Common Errors
Common mistakes related to fractions and decimals that electricians must avoid:
- Backstab connections
- Push-in connections on receptacles fail more often than screw terminals, poor practice though not a code violation
- Wrong breaker size
- Using 20A breaker on 14AWG circuit (max 15A per 240.4(D))
- Improper grounding
- Bootleg ground (jumping neutral to ground at receptacle) or missing EGC
- Missing GFCI
- Bathroom, kitchen, garage, outdoor, and crawl space receptacles require GFCI per 210.8
Calculation Methods
Calculations for fractions and decimals:
| Formula | Equation | Example |
|---|---|---|
| Voltage drop | VD = (2 x K x I x D) / CM | 20A, 150ft, 12AWG (6530CM): VD = (2 x 12.9 x 20 x 150)/6530 = 11.87V (9.9%) |
| Ohms law | E = I x R | 120V circuit with 10 ohm load: I = 120/10 = 12A |
Assessment Techniques
Numerical representations of parts of a whole essential for measurement and calculation in the trades. Tested on the IBEW aptitude exam. Electricians use these daily for conduit measurements and load calculations.
Relevant formula: Ohms law is E = I x R. Variables: E (voltage in volts), I (current in amps), R (resistance in ohms).
Why It Matters
Tested on the IBEW aptitude exam. Electricians use these daily for conduit measurements and load calculations.
Related Terms
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