Calculating Potential difference (X Ray tube)

In summary, the potential difference can be found by dividing the kinetic energy of an electron (acquired by moving through the potential difference) by the charge of an electron. In this case, if the acquired kinetic energy is 75 keV, then the potential difference is 75,000 V. It is important to always write out units when working with equations to ensure accuracy and avoid confusion.
  • #1
axer
35
4

Homework Statement



If the electrons hit the tungsten target with an energy of 75 keV, find the potential difference.

Homework Equations

The Attempt at a Solution


I tried this: (W=eV)
V=W/Q
V=eV/Q
V=75,000/1.6*10-19
V= 4.6*1023 V,

This seems wrong because all examples in my textbook show V is in the thousands but not this big..
 
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  • #2
An electron that moves through a potential difference of 1 Volt acquires kinetic energy of 1 eV. Therefore an electron that moves through a potential difference of 75 keV acquires kinetic energy of ... ?
 
  • #3
kuruman said:
Therefore an electron that moves through a potential difference of 75 keV acquires kinetic energy of ... ?
Thanks for your quick reply, in the question the potential difference was not given and must be calculated. IIm just confused why you said pd of 75keV. Thanks
 
  • #4
axer said:
Thanks for your quick reply, in the question the potential difference was not given and must be calculated. IIm just confused why you said pd of 75keV. Thanks
I wrote pd of 75 keV not 75 eV. Let me restate this. The kinetic energy of an electron starting from rest and moving through a pd of 1 V is 1 eV. In other words, the electron trades potential energy for kinetic energy as it moves from a region of high potential energy to a region of low potential energy. What if the acquired linetic energy is 75 keV (75,000 eV) instead of just 1 eV?
 
  • #5
kuruman said:
I wrote pd of 75 keV not 75 eV. Let me restate this. The kinetic energy of an electron starting from rest and moving through a pd of 1 V is 1 eV. In other words, the electron trades potential energy for kinetic energy as it moves from a region of high potential energy to a region of low potential energy. What if the acquired linetic energy is 75 keV (75,000 eV) instead of just 1 eV?
Thanks, so by my understand of your reply, 1 eV = (1.6*10-19) (1 V)

So if we had 75,000 eV, then the potential difference is also 75,000.
Answer: 75,000 V.

Right?
 
  • #6
axer said:
V=75,000/1.6*10-19
To rsetate what is being hintef at, this would be the potential difference (in volts) if the energy was 75 kJ, not 75 keV. 1 J is not 1 eV. Units are important, never neglect them and always write them out!
 
  • #7
axer said:
1 eV = (1.6*10-19) (1 V)
No! Electron volts is a unit of energy, not a unit of potential difference! Units!
 
  • #8
Orodruin said:
No! Electron volts is a unit of energy, not a unit of potential difference! Units!
Ok i see.. so 1 eV= 1.6*10-19 J

75 keV = 1.6*10-19 (75000)
= 1.2*10-14 J.

this is the energy in Joule of an electron with an energy of 75 keV.

If right.. How do I use it to find V?

If I am being wrong/confusing, would you please show me the answer so I can find where I am thinking wrong. Thanks!
 
  • #9
So you have found that 75 keV is 1.2×10-14J. Use energy conservation and the equation W = eV that you quoted in post #1 to find V. The result may be surprising but not a coincidence.
 
  • #10
axer said:
Ok i see.. so 1 eV= 1.6*10-19 J
Right, now go back to the relation that expresses the energy gained in terms of the charge and the potential difference. What does it tell you?
axer said:
V=W/Q
 
  • #11
so V=1.2*10-14/1.6*10-19
V= 75.000 V
Oh, wait is it actually 75,000... this apply to all questions when given eV and asked to find V.

Thanks both!
 
  • #12
axer said:
so V=1.2*10-14/1.6*10-19
V= 75.000 V
Oh, wait is it actually 75,000... this apply to all questions when given eV and asked to find V.

Thanks both!
Yes, but again, always write out the units. Note that you had the right answer in #5, but you got it in a way that was not completely waterproof. Always write out your units, not only will it let you check that your answer has the correct units, but it is particularly useful to get your argument correct.
 

What is potential difference in an X-ray tube?

Potential difference in an X-ray tube is the difference in electrical potential between the cathode and anode, which creates an electric field to accelerate electrons towards the anode. It is also known as voltage or electrostatic potential.

How is potential difference calculated in an X-ray tube?

Potential difference can be calculated using the formula V = I x R, where V is the potential difference, I is the current, and R is the resistance. In an X-ray tube, the potential difference is determined by the voltage applied to the tube.

What is the importance of potential difference in an X-ray tube?

Potential difference is crucial in an X-ray tube as it determines the speed and energy of the electrons, which in turn affects the quality and intensity of the X-ray beam produced. It also plays a role in controlling the exposure time and dose received by the patient.

What factors can affect potential difference in an X-ray tube?

The main factors that can affect potential difference in an X-ray tube include the voltage applied, the distance between the cathode and anode, and the type of material used for the anode. Additionally, any changes in the electrical circuit, such as a decrease in resistance, can also affect potential difference.

How is potential difference adjusted in an X-ray tube?

Potential difference can be adjusted by changing the voltage applied to the X-ray tube. This can be done manually by the operator or automatically through the use of exposure control systems. The voltage can typically range from 50-150 kV for diagnostic X-ray tubes.

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