[2.5] Power rating & energy consumption

Summary

The video explains the concept of power ratings and energy consumption in electrical appliances, highlighting how power ratings indicate the energy used per second. It provides examples of common household appliances, illustrating that air conditioners are the most expensive to run due to their high power ratings. The relationship between power, time, and energy is outlined, emphasizing the calculation of electricity costs using kilowatt hours. An example demonstrates how to calculate the cost of running a 1500-watt electric iron for 30 minutes at a specified tariff rate, culminating in a practical understanding of electricity expenses.

Takeaways

• ⚡ Appliances have a power rating marked on them, indicating energy consumption per second.
• 🫖 An electric kettle rated at 1,100 to 1,200 watts uses between 1,100 and 1,200 joules per second.
• 💡 Electric lamps typically have low power ratings, making them inexpensive to operate.
• ❄️ Air conditioners are the most costly appliances to run due to their high power ratings and long usage times.
• 🧮 Electrical energy can be calculated using the formula E = P × T, where E is energy in joules, P is power in watts, and T is time in seconds.
• 🔌 Energy is often measured in kilowatt-hours (kWh), useful for calculating electricity costs.
• 💵 One kilowatt-hour is defined as the energy used by a one-kilowatt appliance in one hour.
• 🧾 The cost of electricity is calculated using a tariff rate for each unit consumed.
• 🧑‍🏫 Example: A 1,500 watt electric iron used for 30 minutes consumes 0.75 kWh.
• 💰 At a unit price of 21.8 cents per kWh, the cost for running the electric iron is 18.75 cents.

Q & A

What is a power rating on an electrical appliance?

The power rating marked on an electrical appliance indicates the amount of electrical energy it uses per second, expressed in watts.

How does the power rating affect the cost of running an appliance?

Appliances with higher power ratings consume more electrical energy, leading to higher costs when they are used, especially if they are operated for extended periods.

What is the formula to calculate electrical energy consumption?

The electrical energy consumed can be calculated using the formula E = P × T, where E is energy in joules, P is power in watts, and T is time in seconds.

What is a kilowatt hour (kWh)?

A kilowatt hour (kWh) is the unit of energy used to measure electricity consumption, representing the energy used by a one-kilowatt appliance running for one hour.

How do you calculate the cost of electricity usage?

The cost of electricity can be calculated by multiplying the energy used in kWh by the tariff rate (cost per unit of electricity).

Why are air conditioners considered expensive to run?

Air conditioners have high power ratings and are often operated for long durations, which significantly increases their energy consumption and associated costs.

What is the significance of the tariff rate in electricity billing?

The tariff rate is the cost per unit of electricity, and it determines how much a consumer will pay for their electricity usage, calculated based on the kWh consumed.

If an electric iron rated at 1500 watts is used for 30 minutes, how much energy does it consume?

The electric iron uses 0.75 kilowatt hours (kWh) or 0.75 units of energy when used for 30 minutes.

How much would it cost to run a 1500-watt electric iron for 30 minutes at a rate of 21.8 cents per kWh?

The cost would be approximately 18.75 cents for running the electric iron for 30 minutes.

What are some examples of appliances with low power ratings?

Electric lamps typically have low power ratings and are generally not expensive to run compared to high-power appliances like air conditioners.