Physics
- Resources
- Joe Wolf Educational pages Intro on physics concepts, physclips, related educational works.
- Classical Physics lectures
- Mechanics Joe wolf coursera
- Physclips Physics animation and great introduction to high school physics concepts Courses
- Electric motors and generators Intro Motors Courses
- High school physics Faqs Good question and answers to many problems
- AC circuits Courses
- Hyper physics Georgia tech Index of physical constant and explanations
- Calculus, integral, differentiation introduction for physics #Math Courses learning
- Einstein and light relativity concepts
- Lessons in electric AC circuits
- Dynamics
- []
- Notes
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Terminology
- **The specific heat capacity **is defined as the quantity of heat (J) absorbed per unit mass (kg) of the material when its temperature increases 1 K (or 1 °C), and its units are J/(kg K) or J/(kg °C).
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Temperature rise of mass from energy transfer over time.
- The ratio between heat and a substance’s temperature rise is its specific heat capacity. This factor, along with the substance’s mass and the length of time during which power acts on it, lets you convert the substance’s wattage to its final temperature, measured in degrees.
- Multiply the wattage acting on the substance by the time it spends acting on it. For instance, if a power of 2,500 watts runs for 180 seconds: 2,500 × 180 = 450,000 joules of energy
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Divide this answer by the substance’s mass, measured in grams. For instance, if you heat 2,000 grams of a substance: 450,000 ÷ 2,000 = 225
- Divide this result by the substance's specific heat capacity. For instance, if you are calculating the temperature rise in water, which has a specific heat capacity of 4.186 j/g K: 225 ÷ 4.186 = 53.8
- This is the number of degrees Celsius by which the object's temperature rises.
- Specific question: The hot tub system has a volume of 4.5 m3 and is filled with water at a temperature of 28 °C. The heater transfers thermal energy to the water at a rate of 2.7 kW while a pump circulates the water. Assume that no heat is transferred to the surroundings. Calculate the rise in water temperature that the heater could produce in 1.0 hour. Density of water = 1000 kg m^-3 . Specific heat capacity of water = 4200 J kg–1 K–1
- We begin with the **specific heat capacity equation: Energy = Mass x Specific heat capacity(S.H.C) x Tempchange.** Rearranging for Temperature change we get: **TempChange = Energy/ (Mass x S.H.C).**
- We can observe that the volume and density is given and using the equation Mass = Volume x Density , we can calculate the mass by doing 4.5 x 1000 = 4500Kg.
- Now we need energy. To do this we are given the power and time. Relating them by using Power = Energy/Time and hence **Energy = Power x Time **we can input the given values to arrive at 2.7 x 1000 x 3600 = 9720000J.
- Now we just input the values we have found into the equation for temperature change giving us:Temperature Change = 9720000 / ( 4500 x 4200) = 0.51 K. Throughout, make sure to check the units of the values used
- Energy is in Joules. So Power must me in Joules per Second (Watts) and Time must therefore be in Seconds.This is why the power is multiplied by 1000 for example as kW is the unit for 1000 Watts and the Time is converted from 1 hour to 60 x 60 seconds = 3600 seconds.
Notes mentioning this note
Physics
Resources Joe Wolf Educational pages Intro on physics concepts, physclips, related educational works. Classical Physics lectures Mechanics Joe wolf coursera...