Test Your Knowledge of Electricity
from the Technology Interface Techtips

How much do you know about the electricity coming into your home or office to your wall outlet? This Technology Interface TechTip takes you through some basic questions about your AC wall outlet. The answers to all questions are provided within the document. Just click where instructed to see the answer.

This is a drawing of the standard AC outlet used in the United States.

1. What are the names for terminals A,B,and C?

2. Do you know why terminal A is larger than terminal B?

3. What is a polarized plug?

4. Identify the following voltages:
VAB= _________
VAC= _________
VBC= _________

5. Why is the receptacle sometimes called a 110V outlet and other times a 120V outlet?

Click here to see the answers.

Answers to the Electricity Questions

1. Terminal A - Neutral / Terminal B - Hot / Terminal C - Ground

2. Terminal A is larger than terminal B so that a 2-prong plug remains properly "polarized". Neutral stays neutral and Hot stays Hot.

3. The term "polarized" plug refers to the answer in question 2.

4. VAB= 120 VAC
VAC= 0.0 VAC
VBC= 120 VAC

5. The electrical utilities in North America are required to feed a split phase 240V (+/- 5%) to your home. Your house receives a 120V (+/- 5%) feed to each leg. Also, the electrical power distribution varies from location to location depending on line loss which causes the variations in line voltages at the AC outlet. Basically, all electrical utilities output the same voltage. Over the years, the AC wall outlet has been identified as 110/115/117/120. Along the same line, 220 and 240 are equivalent.