Understanding Physics Units: kWh, Joules, and Electric Current

This question asks us to evaluate the correctness of two statements related to physics units: energy conversion (kilowatt-hour to Joules) and the SI unit of electric current.

Analyzing Statement I: 1 kWh = 3.6 × 10⁶ J

Statement I talks about the conversion between kilowatt-hour (kWh) and Joules (J). Kilowatt-hour is a commonly used unit of electrical energy, while the Joule is the standard SI unit of energy. Let's verify this conversion.

• 1 kilowatt (kW) is a unit of power, equal to 1000 Watts (W).
• 1 hour (h) is a unit of time, equal to 3600 seconds (s).
• Energy is defined as Power × Time.

Therefore, 1 kilowatt-hour can be calculated as:

\(1 \text{ kWh} = 1 \text{ kW} \times 1 \text{ h}\)

\(1 \text{ kWh} = 1000 \text{ W} \times 3600 \text{ s}\)

\(1 \text{ kWh} = 3,600,000 \text{ Ws}\)

Since the unit of power (Watt) is defined as 1 Joule per second (1 W = 1 J/s), the unit Ws is equivalent to Joules (J).

\(1 \text{ Ws} = 1 \frac{\text{J}}{\text{s}} \times 1 \text{ s} = 1 \text{ J}\)

So, \(1 \text{ kWh} = 3,600,000 \text{ J}\).

In scientific notation, \(3,600,000 \text{ J}\) is written as \(3.6 \times 10^6 \text{ J}\).

\(1 \text{ kWh} = 3.6 \times 10^6 \text{ J}\)

Thus, Statement I is correct.

Analyzing Statement II: The SI unit of electric current is the ampere

Statement II concerns the standard unit for measuring electric current in the International System of Units (SI). The SI system defines fundamental units for various physical quantities.

• Electric current is the rate of flow of electric charge.
• The SI unit of electric current is indeed the ampere (A). It is one of the seven base units of the SI system.
• One ampere is defined as the flow of one coulomb of charge per second (\(1 \text{ A} = 1 \text{ C/s}\)). More precisely, the ampere is defined based on the force between two parallel current-carrying conductors.

Therefore, Statement II is correct.

Conclusion on Statement Correctness

Based on our analysis:

• Statement I: \(1 \text{ kWh} = 3.6 \times 10^6 \text{ J}\) is correct.
• Statement II: The SI unit of electric current is the ampere is correct.

Since both statements are correct, the correct option is the one that indicates both I and II are correct.

Revision Table: Physics Units & Conversions

Here is a quick reference for the units discussed:

• Energy Unit (Commercial): Kilowatt-hour (kWh)
• Energy Unit (SI): Joule (J)
• Conversion: \(1 \text{ kWh} = 3.6 \times 10^6 \text{ J}\)
• Electric Current Unit (SI): Ampere (A)

Additional Information: Understanding Energy and Current Units

The kilowatt-hour (kWh) is a practical unit often used for billing electricity consumption because it represents a significant amount of energy compared to a Joule, making it easier to track usage over time (like a month).

The ampere (A) is named after André-Marie Ampère, one of the founders of the study of electromagnetism. Its definition is crucial for electrical circuit analysis and design.

Understanding the relationships between power, energy, time, current, and charge is fundamental in physics and electrical engineering.