Calculating Q (dot): William Needs Help

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In summary, the conversation discusses the calculation of power (Q(dot)) using voltage and current, and the units associated with it (Watts/Joules per second/Newtons per meter per second). The conversation ends with a thank you and confirmation of understanding.
  • #1
skaboy607
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Hi

Wondering if someone could help me satisfy my curiosity. Hopefully a very simple for someone who knows. I have been given values for Voltage and Current. To calculate Q (dot), I know Q(dot)=V * A. The units for this are Watts / J/s / Nm/s.. How can Voltage multiplied by a current provide these units?

Thanks

William
 
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  • #2
Welcome to PF!

Hi William! Welcome to PF! :smile:

From electric units in the PF Library

Power = voltage.current = energy/time (dim. [itex]ML^2/T^3[/itex]):

[tex]\text{W}\ \equiv\ \text{watt}\ \equiv\ \frac{\text{J}}{\text{s}}\ \equiv\ \frac{\text{joule}}{\text{second}}\ \equiv\ \frac{\text{N.m}}{\text{s}}\ \equiv\ \frac{\text{Newton.metre}}{\text{second}}\ \equiv\ \text{V.A}\ \equiv\ \text{volt.amp}\ \equiv\ \Omega\text{.A}^2\ \equiv\ \text{ohm.amp}^2[/tex]
 
  • #3
Thank you very much. Good to of joined.

Thats that sorted then, thanks for clearing up.

William
 

1. What is Q (dot) and why is it important?

Q (dot) is a measure of the rate of heat transfer, or the amount of heat energy being transferred per unit time. It is important because it helps us understand and predict how quickly a system will reach thermal equilibrium.

2. How do you calculate Q (dot)?

To calculate Q (dot), you need to know the heat transfer coefficient (h), the surface area (A), and the temperature difference (ΔT) between the two objects. The formula is Q (dot) = h * A * ΔT.

3. What are the units for Q (dot)?

The units for Q (dot) are watts (W) or joules per second (J/s).

4. Can Q (dot) be negative?

Yes, Q (dot) can be negative if heat is being transferred from a hotter object to a colder object, resulting in a decrease in temperature. This is known as heat loss.

5. How is Q (dot) used in real-world applications?

Q (dot) is commonly used in engineering and physics to analyze and design systems involving heat transfer, such as in building insulation, refrigeration systems, and power plants. It is also used in chemistry and biology to study thermal reactions and metabolic processes.

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