Chapter 12 Exercises

These exercises are designed to build practical understanding of residential electrical systems. All exercises involve safe observation, calculation, or bill-reading — none involve touching live wires or opening electrical panels.

Exercise 1: Ohm's Law in Your Home

Objective: Apply voltage, current, and resistance concepts to real household appliances.

What you need: A few appliance labels or owner's manuals, a calculator.

Instructions:

Find the wattage listed on the nameplate or label of five appliances in your home. For each appliance, calculate: - The current it draws (amps = watts ÷ voltage) - Assume 120V for small appliances, 240V for ranges/dryers/water heaters

Record your answers in a table:

Appliance Voltage Wattage Current Draw (A)

Questions: 1. Which appliance draws the most current? 2. If your kitchen is on a 20-amp circuit, which of your appliances — if running simultaneously — would approach or exceed that limit? 3. A 1,200-watt hair dryer and a 1,500-watt space heater are both plugged into outlets on the same 15-amp circuit. Calculate the total current draw. What will happen?

Exercise 2: Locate and Identify Your Service Entrance

Objective: Physically locate and identify the components of your home's electrical service entrance.

What you need: Your own home, safe observation from ground level.

Safety note: This exercise is observation only. Do not touch any wires, the meter, or any service entrance equipment.

Instructions:

  1. Walk around the exterior of your home and find where the utility wires connect to your home (the weatherhead or service entrance mast for overhead service, or the conduit entering from underground for underground service).

  2. Trace the path from the weatherhead/entry point to the meter. Locate the meter.

  3. From the outside, observe: Is the service entrance in good condition? Is the conduit straight and properly attached? Is the meter socket free of rust, damage, or pest intrusion?

  4. Identify whether your service is overhead (wires coming from a pole) or underground (conduit from below grade).

Record: - Location of weatherhead or service entry - Location of meter - Service type (overhead/underground) - Any visible damage or concerns worth noting

Questions: 1. Who is responsible for maintaining the wires from the utility pole to your meter? Who is responsible from the meter into your home? 2. If you saw a tree branch resting on the service drop wires, who should you call?

Exercise 3: Read Your Electric Meter

Objective: Read an analog or digital electric meter and understand what it measures.

What you need: Access to your meter (safe exterior observation).

Safety note: Observe the meter from a safe distance. Do not open the meter socket.

Instructions:

  1. Locate your meter. Record the current reading (date and time).

  2. If it's a digital smart meter: read the kWh total displayed.

  3. If it's an analog dial meter: practice reading each dial. Record what you read from each dial, left to right, remembering that adjacent dials rotate in opposite directions. When a pointer is between numbers, record the lower number.

  4. Compare your reading to your most recent electric bill. Does the reading seem consistent with the billed consumption for the billing period?

  5. Return to read the meter 24 hours later. Calculate your home's approximate daily consumption in kWh.

Questions: 1. At your home's 24-hour consumption rate, what is your approximate annual consumption? 2. At your local electricity rate (found on your bill), what is the approximate daily cost of electricity for your home?

Exercise 4: Deconstruct Your Electric Bill

Objective: Identify and understand every line item on your electric bill.

What you need: Your most recent electric bill (paper or digital).

Instructions:

  1. Find the following on your bill and record them: - Total kWh consumed this billing period - Billing period (number of days) - Average daily consumption (kWh ÷ days) - Rate per kWh (may be buried in the rate schedule) - Fixed charges (customer/service charge) - Any variable charges (fuel adjustment, etc.) - Taxes and fees - Total amount due

  2. Calculate: What percentage of your total bill is the energy charge (kWh × rate)?

  3. Compare your consumption to the same month last year (if shown on the bill). Has it gone up, down, or stayed the same?

  4. Identify your rate type: flat, tiered, or time-of-use? (Check the bill details or your utility's website.)

Questions: 1. If you reduced your consumption by 10%, how much would you save per month in dollars? 2. What is the single largest driver of your electricity bill (hint: look at seasonal variation — air conditioning in summer, heating in winter)?

Exercise 5: Calculate the Cost of Your Appliances

Objective: Estimate the annual electricity cost of specific appliances in your home.

Formula: Annual cost = (Wattage ÷ 1,000) × Hours per year × $/kWh

Instructions:

Using your electricity rate from Exercise 4, calculate the annual cost of:

  1. Your refrigerator (find the wattage on the label inside, typically 100–200W; assume it runs about 30% of the time — multiply by 0.30 to get effective continuous draw)

  2. Your television (find the wattage in the manual or on the label; estimate your daily viewing hours)

  3. Your water heater (if electric; find the wattage — typically 4,500W; estimate it runs about 3 hours per day)

  4. Your air conditioner or heat pump (find the wattage or tonnage; 1 ton = approximately 1,200W for a modern efficient unit; estimate seasonal hours)

  5. Any appliance you suspect is high-consuming

Questions: 1. Which appliance costs the most to run annually? 2. If your refrigerator is 15 years old (consuming 200W average) vs. a new efficient model (100W average), what is the annual savings from upgrading? How many years to payback a $600 appliance purchase? 3. What would be the annual savings if you shifted your electric vehicle charging entirely to overnight off-peak hours if your utility charges $0.08/kWh overnight vs. $0.22/kWh during peak hours (assume 10,000 miles/year at 3.5 miles/kWh)?

Exercise 6: Identify Your Main Disconnect

Objective: Locate and understand the main electrical disconnect for your home.

What you need: Your home's electrical panel (observation only, door may be opened, cover stays on).

Safety note: You may open the panel door to observe the breakers. Do not remove the panel cover (the metal plate behind the breakers). Do not touch any wiring.

Instructions:

  1. Locate your main electrical panel.

  2. Open the panel door. Look for the main circuit breaker — typically a large double-pole breaker at the top of the panel, rated for your service size (100A, 150A, 200A).

  3. Record the main breaker's rating (in amps).

  4. Note: Is the panel full? Are there empty breaker slots? Count them.

  5. Look for the panel manufacturer and model information, usually printed inside the panel or on the inside of the door.

  6. Look for the panel's maximum amperage rating (may be printed on the panel label).

Questions: 1. What is the amperage of your main breaker? Based on Chapter 12, is this service size appropriate for a modern home? 2. If you were to add an EV charger (requiring a 50-amp circuit), does your panel appear to have the physical space? 3. Who would you call to find out whether your panel has sufficient capacity for a major new electrical load?

Exercise 7: The Water Analogy — Where It Helps and Where It Doesn't

Objective: Deepen conceptual understanding by testing the water analogy against real electrical scenarios.

Instructions:

For each electrical scenario below, explain it first using the water analogy, then identify whether the analogy holds or breaks down:

  1. A short circuit causes a massive current surge that trips the breaker instantly.

  2. A hair dryer and a space heater on the same 15-amp circuit together draw 20 amps, tripping the breaker after a few minutes.

  3. A 240-volt dryer uses less current than a 120-volt device of the same power.

  4. A loose wire connection creates heat at that point even though the rest of the wire is fine.

  5. A GFCI outlet can detect even 5 milliamps of current flowing to ground and trip instantly.

For each: Which aspects of the water analogy translate well? Which break down?

Exercise 8: Grounding and Bonding Inspection

Objective: Visually identify grounding and bonding components in your home.

What you need: A flashlight, your home.

Safety note: Observation only. Do not touch any electrical components.

Instructions:

  1. Ground rods: Go outside and look around your home's foundation, especially near the electrical panel. Look for a copper or copper-clad rod protruding from the ground with a clamp and copper wire attached. Record whether you can find one (or two).

  2. Bonding at water heater: Locate your water heater. Look for a bare copper wire or green wire connected to the water supply pipes near the heater, running to a clamp on the pipe. This is a bonding jumper.

  3. Main panel ground wire: Look for the main panel. Can you see a bare copper wire leaving the bottom or side of the panel and running toward the ground rod location?

  4. Panel neutral and ground bars: Through the open panel door (cover stays on), can you see two distinct bus bars at the bottom of the panel — or just one? In a main panel, neutral and ground may share a bar. In a sub-panel, they must be separate.

Questions: 1. What is the purpose of the ground rod connection? 2. If your home's metal water supply pipes were replaced with PEX plastic piping, why might this affect the grounding system? 3. What is the difference between what grounding does and what bonding does?

Exercise 9: Household Energy Audit — Vampire Loads

Objective: Estimate the standby power ("vampire load") of devices in your home and calculate the annual cost.

Instructions:

Walk through your home and list every device that: - Has a digital clock or display when "off" - Has a remote control (meaning it's listening for a signal) - Has an "instant on" function - Has an external power supply (brick-style charger) - Has a standby light (LED indicator when powered but idle)

Typical standby power draws (use these estimates): - Cable box / DVR: 15–20W - Game console in standby: 10–15W - Smart TV in standby: 1–5W - Microwave with clock: 2–3W - Coffee maker with clock: 1–2W - Each device charger (phone, tablet): 0.5–2W - Laser printer: 8–15W - Stereo/home theater receiver: 5–20W

Calculate: 1. Total estimated standby wattage for your home 2. Annual kWh (standby watts × 8,760 hours ÷ 1,000) 3. Annual cost at your electricity rate

Questions: 1. What percentage of your monthly bill is estimated standby/vampire consumption? 2. What is the simplest intervention to reduce vampire loads? 3. If you used a smart power strip on your entertainment center that cuts power to the TV, cable box, game console, and stereo when the TV is off, how much would you save annually?

Exercise 10: AC vs. DC in Your Home

Objective: Identify devices in your home that convert AC to DC and devices that run directly on AC.

Instructions:

Walk through your home and categorize devices into: - Runs on AC directly: Lights with incandescent or halogen bulbs, heating elements (toaster, coffee maker, electric stove elements, electric dryer heating element), motors you can hear humming (HVAC blower, refrigerator compressor), fluorescent lights (older type) - Converts AC to DC internally: All devices with internal rechargeable batteries, computers and laptops (power supply converts), LED lights (LED driver converts), televisions, smart home devices, anything with a transformer brick - Requires low DC only: Smoke detectors, battery-powered devices, doorbells (often 12–24V AC through a transformer, but some use DC)

Questions: 1. In your home, which category has more devices — AC-direct or AC-to-DC? 2. Why does a laptop power supply (AC to DC converter) often feel warm to the touch? 3. If you have a solar panel system on your home, at what point does the DC from the panels become AC for your home's circuits?

Exercise 11: Explore Your Utility's Rate Structure

Objective: Understand the rate options available from your utility and evaluate whether your current rate is optimal.

What you need: Your utility company's website or your electric bill.

Instructions:

  1. Look up your utility's available residential rate plans. Most offer more than one.

  2. For each plan, identify: - Is it flat rate, tiered, or time-of-use? - What is the $/kWh rate (or the schedule for TOU plans)? - Are there any minimum charges or fixed fees?

  3. Using your actual consumption data from your bill, estimate what your bill would have been under each available rate plan.

  4. If your utility offers a TOU rate, identify the peak and off-peak hours. Which of your high-consuming activities (running dishwasher, doing laundry, charging an EV) could be shifted to off-peak hours?

Questions: 1. Is there a rate plan available to you that would reduce your bill based on your usage patterns? 2. If you had a Level 2 EV charger and charged only overnight from 11 PM to 7 AM on a TOU plan, vs. plugging in whenever convenient, how much would you save annually? (Estimate 12,000 miles/year at 3 miles/kWh) 3. What technology or change in habits would be required to take advantage of a TOU rate?

Exercise 12: Write Your Home's Electrical Profile

Objective: Synthesize the chapter's content into a single-page summary of your home's electrical situation.

Instructions:

Based on your work in Exercises 2, 3, 4, 5, and 6, write a one-page "electrical profile" of your home that includes:

  • Service type and size (amps)
  • Panel manufacturer, approximate age
  • Monthly average kWh consumption
  • Monthly average cost
  • Top three energy-consuming appliances by estimated annual cost
  • Any concerns identified during exercises (full panel, old service size, etc.)
  • One energy efficiency improvement you could make that would have the greatest impact on your bill

This profile will be useful context for Chapter 13 (panel capacity) and Chapter 14 (outlets and wiring) as well.