#$&* course phy122 3/31 7 027. *********************************************
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Given Solution: The change in potential is final potential - initial potential = -55 V - (135 V) = -190 V, so the change in the potential energy of the proton is -190 V * 1.6 * 10^-19 C = -190 J / C * 1.6 * 10^-19 C = -3.0 * 10^-17 J. In the absence of dissipative forces this is equal and opposite to the change in the KE of the proton; i.e., the proton would gain 3.09 * 10^-17 J of kinetic energy. Change in potential energy is equal and opposite to the work done by the field on the charge, so the field does 3.0 * 10^-17 J of work on the charge. Since the charge of the proton is equal in magnitude to that of an electron, he work in electron volts would be 180 volts * charge of 1 electron= 180 eV. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): ------------------------------------------------ Self-critique Rating: ********************************************* Question: `qQuery Principles and General Physics 17.8: Potential difference required to give He nucleus 65.0 keV of KE. YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY Your Solution: 65.0 keV is 65.0 x 10 ^3 eV or 6.50 x 10 ^4 eV The chatge on a He nucleus is +2e (helium has 2 protons) For every volt of potential difference, the HE nucleus would gain 2 eV of kinetic energy. To gain 6.50 x 10 ^4 of energy the voltage difference would therefore be ˝ of 6.50 x 10^4 voles= 3.35 x 10 ^4 voles confidence rating #$&*: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Given Solution: 65.0 keV is 65.0 * 10^3 eV, or 6.50 * 10^4 eV, of energy. The charge on a He nucleus is +2 e, where e is the charge on an electron. So assuming no dissipative forces, for every volt of potential difference, the He nuclues would gain 2 eV of kinetic energy. To gain 6.50 * 10^4 eV of energy the voltage difference would therefore be half of 6.50 * 10^4 voles, or 3.35 * 10^4 volts. STUDENT QUESTION I didn’t convert the keV into eV. What do these units even mean?? INSTRUCTOR RESPONSE k means 'kilo'; so a keV is 10^3 eV. An electron volt is the PE change of an electron as it moves through a PE change of +1 volt. A Joule is the PE change of a Coulomb of negative charge as it moves through a PE change of +1 volt. Since the charge of an electron has magnitude 1.6 * 10^-19 Coulomb, an electron volt is 1.6 * 10^-19 Joules. Within the electron shell of an atom, and in many other applications, we are dealing with charges of in small whole-number multiples of 1.6 * 10^-19 Coulomb, moving between points where potential changes are anywhere from a few millivolts to a few volts. The associated energy changes are more easily thought of in terms of electron volts (typical values might range from .001 eV to around 100 eV) than ergs or Joules (where the same range might be, for example, 10^-17 Joules to 10^-22 Joules). Numbers between .001 and 100 are easy to think about, an relate easily to the energy of a single electron moving through a potential difference of a single volt. Numbers like 10^-17 and 10^-22 are harder to imagine. STUDENT QUESTION I understand the formula, but didn’t know where to find He? May have missed it in the notes……anyway INSTRUCTOR RESPONSE It is assumed to be general knowledge that a helium nucleus contains 2 protons, each with a positive charge equal in magnitude to the electron charge. However not everyone remembers this, and without this knowledge it would be difficult to get the entire solution. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): " Self-critique (if necessary): ------------------------------------------------ Self-critique rating: ********************************************* Question: `qQuery Principles and General Physics 17.8: Potential difference required to give He nucleus 65.0 keV of KE. YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY Your Solution: 65.0 keV is 65.0 x 10 ^3 eV or 6.50 x 10 ^4 eV The chatge on a He nucleus is +2e (helium has 2 protons) For every volt of potential difference, the HE nucleus would gain 2 eV of kinetic energy. To gain 6.50 x 10 ^4 of energy the voltage difference would therefore be ˝ of 6.50 x 10^4 voles= 3.35 x 10 ^4 voles confidence rating #$&*: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Given Solution: 65.0 keV is 65.0 * 10^3 eV, or 6.50 * 10^4 eV, of energy. The charge on a He nucleus is +2 e, where e is the charge on an electron. So assuming no dissipative forces, for every volt of potential difference, the He nuclues would gain 2 eV of kinetic energy. To gain 6.50 * 10^4 eV of energy the voltage difference would therefore be half of 6.50 * 10^4 voles, or 3.35 * 10^4 volts. STUDENT QUESTION I didn’t convert the keV into eV. What do these units even mean?? INSTRUCTOR RESPONSE k means 'kilo'; so a keV is 10^3 eV. An electron volt is the PE change of an electron as it moves through a PE change of +1 volt. A Joule is the PE change of a Coulomb of negative charge as it moves through a PE change of +1 volt. Since the charge of an electron has magnitude 1.6 * 10^-19 Coulomb, an electron volt is 1.6 * 10^-19 Joules. Within the electron shell of an atom, and in many other applications, we are dealing with charges of in small whole-number multiples of 1.6 * 10^-19 Coulomb, moving between points where potential changes are anywhere from a few millivolts to a few volts. The associated energy changes are more easily thought of in terms of electron volts (typical values might range from .001 eV to around 100 eV) than ergs or Joules (where the same range might be, for example, 10^-17 Joules to 10^-22 Joules). Numbers between .001 and 100 are easy to think about, an relate easily to the energy of a single electron moving through a potential difference of a single volt. Numbers like 10^-17 and 10^-22 are harder to imagine. STUDENT QUESTION I understand the formula, but didn’t know where to find He? May have missed it in the notes……anyway INSTRUCTOR RESPONSE It is assumed to be general knowledge that a helium nucleus contains 2 protons, each with a positive charge equal in magnitude to the electron charge. However not everyone remembers this, and without this knowledge it would be difficult to get the entire solution. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): " Self-critique (if necessary): ------------------------------------------------ Self-critique rating: #*&! ********************************************* Question: `qQuery Principles and General Physics 17.8: Potential difference required to give He nucleus 65.0 keV of KE. YYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYYY Your Solution: 65.0 keV is 65.0 x 10 ^3 eV or 6.50 x 10 ^4 eV The chatge on a He nucleus is +2e (helium has 2 protons) For every volt of potential difference, the HE nucleus would gain 2 eV of kinetic energy. To gain 6.50 x 10 ^4 of energy the voltage difference would therefore be ˝ of 6.50 x 10^4 voles= 3.35 x 10 ^4 voles confidence rating #$&*: ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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Given Solution: 65.0 keV is 65.0 * 10^3 eV, or 6.50 * 10^4 eV, of energy. The charge on a He nucleus is +2 e, where e is the charge on an electron. So assuming no dissipative forces, for every volt of potential difference, the He nuclues would gain 2 eV of kinetic energy. To gain 6.50 * 10^4 eV of energy the voltage difference would therefore be half of 6.50 * 10^4 voles, or 3.35 * 10^4 volts. STUDENT QUESTION I didn’t convert the keV into eV. What do these units even mean?? INSTRUCTOR RESPONSE k means 'kilo'; so a keV is 10^3 eV. An electron volt is the PE change of an electron as it moves through a PE change of +1 volt. A Joule is the PE change of a Coulomb of negative charge as it moves through a PE change of +1 volt. Since the charge of an electron has magnitude 1.6 * 10^-19 Coulomb, an electron volt is 1.6 * 10^-19 Joules. Within the electron shell of an atom, and in many other applications, we are dealing with charges of in small whole-number multiples of 1.6 * 10^-19 Coulomb, moving between points where potential changes are anywhere from a few millivolts to a few volts. The associated energy changes are more easily thought of in terms of electron volts (typical values might range from .001 eV to around 100 eV) than ergs or Joules (where the same range might be, for example, 10^-17 Joules to 10^-22 Joules). Numbers between .001 and 100 are easy to think about, an relate easily to the energy of a single electron moving through a potential difference of a single volt. Numbers like 10^-17 and 10^-22 are harder to imagine. STUDENT QUESTION I understand the formula, but didn’t know where to find He? May have missed it in the notes……anyway INSTRUCTOR RESPONSE It is assumed to be general knowledge that a helium nucleus contains 2 protons, each with a positive charge equal in magnitude to the electron charge. However not everyone remembers this, and without this knowledge it would be difficult to get the entire solution. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& Self-critique (if necessary): " Self-critique (if necessary): ------------------------------------------------ Self-critique rating: #*&!#*&!