What are the units for E


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Talia Leano 2H
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What are the units for E

Postby Talia Leano 2H » Sat Oct 17, 2020 8:24 pm

In the equation E = hv? What are the units for E? Also for the equation E(PHOTON) - E(ENERGY REMOVE e-) = E(EXCESS) = Ek(e-) do all of those variables have the same units and if so what are they?

Hannah Biju 1E
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Re: What are the units for E

Postby Hannah Biju 1E » Sat Oct 17, 2020 8:25 pm

Since it is Energy your answer should probably be in Joules. If you use the equation to solve for wavelength your answer should be in meters or nanometers.

Valerie Doan 3I
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Re: What are the units for E

Postby Valerie Doan 3I » Sat Oct 17, 2020 8:33 pm

In the equation E(PHOTON) - E(ENERGY REMOVE e-) = E(EXCESS) = Ek(e-), the units for all energies is Joules (J). For E(PHOTON)=hv, the units for h is Joules*second, and the units for v (frequency) is Hertz. For the kinetic energy equation Ek(e-)=0.5mv^2, mass is in kg and v (velocity) is in meters per second. All the units for these variables are SI units, which means that they are standardized.

Lillian Ma 1I
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Re: What are the units for E

Postby Lillian Ma 1I » Sat Oct 17, 2020 10:01 pm

The unit for energy is joules (J), but another way to think of joules is as kg*(m^2/s^2), which might be easier in this case to cancel out with the other units of the variables in the equation.

Ariel Guan 1H
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Re: What are the units for E

Postby Ariel Guan 1H » Sat Oct 17, 2020 10:03 pm

The units for everything should be in Joules, since they are all Energy. Also remember that 1 Joule = 1 kg m^2 / s^2

John_Tran_3J
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Re: What are the units for E

Postby John_Tran_3J » Sat Oct 17, 2020 10:57 pm

The equation can be manipulated to to solve for either "E" for energy or for "wavelength." When solving for energy, you would use joules. When given the energy at any question, you would have to solve for "wavelength" meaning your units would be in M for meters, the answer should always be in nanometers, so you would have to multiply "M" by 1x10^-9.

Tanner Bartyczak 1K
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Re: What are the units for E

Postby Tanner Bartyczak 1K » Sat Oct 17, 2020 11:48 pm

The units should be joules, which is equal to kg*(m^2/s^2)

Simran Bains 2C
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Re: What are the units for E

Postby Simran Bains 2C » Sun Oct 18, 2020 12:44 am

Energy is measured in Joules. Just remember that Joules can also be measured as kg*(m^2/s^2).

Ven Chavez 2K
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Re: What are the units for E

Postby Ven Chavez 2K » Sun Oct 18, 2020 11:56 am

Joules is the SI unit for energy and in the case of E=hv Energy (Joules) = Planck's constant (Joule*Second) x Frequency (Seconds^-1). The units for Planck's constant is in Joule-second which is the product of joules and seconds. Therefore in the equation, the Seconds will cancel leaving only Joules. Just a heads up, Frequency can be given in the SI unit Hertz (Hz) or the inverse of seconds (s^-1) but these are interchangeable and the value will be the same.

Reese_Gover2K
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Re: What are the units for E

Postby Reese_Gover2K » Sun Oct 18, 2020 12:41 pm

Since E is energy the units should be Joules.

Lauren Strickland 1B
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Re: What are the units for E

Postby Lauren Strickland 1B » Sun Oct 18, 2020 12:46 pm

When the question is talking about energy you should probably use Joules.

Kyle Dizon 3A
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Re: What are the units for E

Postby Kyle Dizon 3A » Sun Oct 18, 2020 8:36 pm

Energy is usually given in Joules after calculations. If you are calculating for wavelength, the problem will often tell you to either give your answer in meters or nanometers.

IshanModiDis2L
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Re: What are the units for E

Postby IshanModiDis2L » Sun Oct 18, 2020 8:42 pm

With your calculations, energy is measured in Joules (J). However, it can also be written as kg*(m^2/s^2) so it helps to be aware of that as well.

Jerry_T
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Re: What are the units for E

Postby Jerry_T » Sun Oct 18, 2020 8:59 pm

Since the units for Planck's constant (h) are Joules second (J.s), the unit for E should Joules (J).

Heidi Buri 2I
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Re: What are the units for E

Postby Heidi Buri 2I » Sun Oct 18, 2020 9:35 pm

Hi! In the equation E=hv, I believe that the units for E are in Joules. The reasoning behind this is because E is the energy of a photon. Since energy is measured in Joules, E would be in Joules.

IreneSeo3F
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Re: What are the units for E

Postby IreneSeo3F » Sun Oct 18, 2020 11:20 pm

The SI unit for Energy is J(joule) and Joule = kgm^2s^-1. And yes the units are all the same in order for you to subtract from one another. If you are adding/subtracting something, the components must have the same unit!

Maddie Turk Disc 2J
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Re: What are the units for E

Postby Maddie Turk Disc 2J » Wed Oct 21, 2020 11:41 am

Almost always when you are working with energy the units attached will be in joules! Hope this helps:)


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