Final answer:
To calculate the electrical needs of a home, list the wattage of all appliances, use the formula P = IV for power when current is known, and estimate energy consumed by multiplying power by usage time. A toaster has a higher rating than a clock due to its heat generation requirement. Energy cost can then be estimated by also considering the cost per kWh from the utility company.
Step-by-step explanation:
Understanding Electrical Needs through Inequalities
To write inequalities to calculate the electrical needs of a home, you first need to list and sum up the power ratings (in watts) of all the appliances. To illustrate, let's consider an appliance like a toaster which has a higher power rating than a digital clock because a toaster is designed to generate a lot of heat in a short time, which requires more electrical energy compared to the minimal energy needed to power the small LED display of a clock. For a specific appliance, if the operating current (amperes) is known and you assume a household voltage of 120 V, the power rating can be calculated using the formula P = IV (Power = Current x Voltage).
Now let's consider the power consumption over time. Energy consumed (in watt-hours) can be estimated by multiplying the power rating by the time for which the appliance is utilized. For example, if a water heating system has a rating of 9,000 W (P=9x10³W) and it's used for 2 hours a day, the energy consumed would be 18,000 Wh (or 18 kWh) per day.
Lastly, consider the case where the entire light system of a building is left on over the weekend. With our long fluorescent lights rated at 32 W each, we can calculate the total wattage used and then convert this into a cost by multiplying by the number of hours used and the cost per kWh from the utility company.