Adding Field Vectors
About points...
We associate a certain number of points with each exercise.
When you click an exercise into a collection, this number will be taken as points for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit the number of points for the exercise in the collection independently, without any effect on "points by default" as represented by the number here.
That being said... How many "default points" should you associate with an exercise upon creation?
As with difficulty, there is no straight forward and generally accepted way.
But as a guideline, we tend to give as many points by default as there are mathematical steps to do in the exercise.
Again, very vague... But the number should kind of represent the "work" required.
When you click an exercise into a collection, this number will be taken as points for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit the number of points for the exercise in the collection independently, without any effect on "points by default" as represented by the number here.
That being said... How many "default points" should you associate with an exercise upon creation?
As with difficulty, there is no straight forward and generally accepted way.
But as a guideline, we tend to give as many points by default as there are mathematical steps to do in the exercise.
Again, very vague... But the number should kind of represent the "work" required.
About difficulty...
We associate a certain difficulty with each exercise.
When you click an exercise into a collection, this number will be taken as difficulty for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit its difficulty in the collection independently, without any effect on the "difficulty by default" here.
Why we use chess pieces? Well... we like chess, we like playing around with \(\LaTeX\)-fonts, we wanted symbols that need less space than six stars in a table-column... But in your layouts, you are of course free to indicate the difficulty of the exercise the way you want.
That being said... How "difficult" is an exercise? It depends on many factors, like what was being taught etc.
In physics exercises, we try to follow this pattern:
Level 1 - One formula (one you would find in a reference book) is enough to solve the exercise. Example exercise
Level 2 - Two formulas are needed, it's possible to compute an "in-between" solution, i.e. no algebraic equation needed. Example exercise
Level 3 - "Chain-computations" like on level 2, but 3+ calculations. Still, no equations, i.e. you are not forced to solve it in an algebraic manner. Example exercise
Level 4 - Exercise needs to be solved by algebraic equations, not possible to calculate numerical "in-between" results. Example exercise
Level 5 -
Level 6 -
When you click an exercise into a collection, this number will be taken as difficulty for the exercise, kind of "by default".
But once the exercise is on the collection, you can edit its difficulty in the collection independently, without any effect on the "difficulty by default" here.
Why we use chess pieces? Well... we like chess, we like playing around with \(\LaTeX\)-fonts, we wanted symbols that need less space than six stars in a table-column... But in your layouts, you are of course free to indicate the difficulty of the exercise the way you want.
That being said... How "difficult" is an exercise? It depends on many factors, like what was being taught etc.
In physics exercises, we try to follow this pattern:
Level 1 - One formula (one you would find in a reference book) is enough to solve the exercise. Example exercise
Level 2 - Two formulas are needed, it's possible to compute an "in-between" solution, i.e. no algebraic equation needed. Example exercise
Level 3 - "Chain-computations" like on level 2, but 3+ calculations. Still, no equations, i.e. you are not forced to solve it in an algebraic manner. Example exercise
Level 4 - Exercise needs to be solved by algebraic equations, not possible to calculate numerical "in-between" results. Example exercise
Level 5 -
Level 6 -
Question
Solution
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Video
\(\LaTeX\)
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Exercise:
The positions of two positive po charges q_AqaO and q_BqbO are are given by vecr_AraxO|rayOunitcm and vecr_BrbxO|rbyOunitcm respectively. Calculate the electric field vector of their combined electric field at po P with vecr_PPxO|PyOunitcm.
Solution:
The strategy is as follows see figure below: itemize item find the vectors from q_A and q_B to the po P item determine the partial fields vecE_A and vecE_B as vectors using the formula for the field of a po charge item add the partial field vectors itemize center includegraphicswidth.mm#image_path:adding-field-vectors# center The partial electric field vectors at po P are given by E_A k_C fracQr_AP^fracvecr_APr_APk_C fracQ|vecr_P-vecr_A|^ leftvecr_P-vecr_Aright E_B k_C fracQr_BP^fracvecr_BPr_BPk_C fracQ|vecr_P-vecr_B|^ leftvecr_P-vecr_Bright With vecr_P-vecr_A pmatrix r_P x-r_A x r_P y-r_A y pmatrix pmatrix PxO-rax PyO-rayO pmatrixunitcm pmatrix raPxS raPyP pmatrixunitcm vecr_P-vecr_B pmatrix r_P x-r_B x r_P y-r_B y pmatrix pmatrix PxO-rbx PyO-rbyO pmatrixunitcm pmatrix rbPxS rbPyS pmatrixunitcm and |vecr_P-vecr_A| sqrtraPxS^+raPyP^unitcmraPunitcm |vecr_P-vecr_B| sqrtrbPxS^+rbPyS^unitcmrbPunitcm we find vecE_A kCtimesfracqaraPtimes ^-unitm^timespmatrix raPxS raPySpmatrix times ^-unitm pmatrix EAx EAy pmatrix unitkilonewton/C vecE_B kCtimesfracqbrbPtimes ^-unitm^timespmatrix rbPxS rbPySpmatrix times ^-unitm pmatrix EBx EBy pmatrix unitkilonewton/C The net electric field is the of the partial fields: vecE vecE_A+vecE_B pmatrix EAx EAy pmatrix unitkilonewton/C + pmatrix EBx EBy pmatrix unitkilonewton/C pmatrix Ex Ey pmatrix unitkilonewton/C approx result pmatrix ExP EyP pmatrix unitkilonewton/C
The positions of two positive po charges q_AqaO and q_BqbO are are given by vecr_AraxO|rayOunitcm and vecr_BrbxO|rbyOunitcm respectively. Calculate the electric field vector of their combined electric field at po P with vecr_PPxO|PyOunitcm.
Solution:
The strategy is as follows see figure below: itemize item find the vectors from q_A and q_B to the po P item determine the partial fields vecE_A and vecE_B as vectors using the formula for the field of a po charge item add the partial field vectors itemize center includegraphicswidth.mm#image_path:adding-field-vectors# center The partial electric field vectors at po P are given by E_A k_C fracQr_AP^fracvecr_APr_APk_C fracQ|vecr_P-vecr_A|^ leftvecr_P-vecr_Aright E_B k_C fracQr_BP^fracvecr_BPr_BPk_C fracQ|vecr_P-vecr_B|^ leftvecr_P-vecr_Bright With vecr_P-vecr_A pmatrix r_P x-r_A x r_P y-r_A y pmatrix pmatrix PxO-rax PyO-rayO pmatrixunitcm pmatrix raPxS raPyP pmatrixunitcm vecr_P-vecr_B pmatrix r_P x-r_B x r_P y-r_B y pmatrix pmatrix PxO-rbx PyO-rbyO pmatrixunitcm pmatrix rbPxS rbPyS pmatrixunitcm and |vecr_P-vecr_A| sqrtraPxS^+raPyP^unitcmraPunitcm |vecr_P-vecr_B| sqrtrbPxS^+rbPyS^unitcmrbPunitcm we find vecE_A kCtimesfracqaraPtimes ^-unitm^timespmatrix raPxS raPySpmatrix times ^-unitm pmatrix EAx EAy pmatrix unitkilonewton/C vecE_B kCtimesfracqbrbPtimes ^-unitm^timespmatrix rbPxS rbPySpmatrix times ^-unitm pmatrix EBx EBy pmatrix unitkilonewton/C The net electric field is the of the partial fields: vecE vecE_A+vecE_B pmatrix EAx EAy pmatrix unitkilonewton/C + pmatrix EBx EBy pmatrix unitkilonewton/C pmatrix Ex Ey pmatrix unitkilonewton/C approx result pmatrix ExP EyP pmatrix unitkilonewton/C
Meta Information
Exercise:
The positions of two positive po charges q_AqaO and q_BqbO are are given by vecr_AraxO|rayOunitcm and vecr_BrbxO|rbyOunitcm respectively. Calculate the electric field vector of their combined electric field at po P with vecr_PPxO|PyOunitcm.
Solution:
The strategy is as follows see figure below: itemize item find the vectors from q_A and q_B to the po P item determine the partial fields vecE_A and vecE_B as vectors using the formula for the field of a po charge item add the partial field vectors itemize center includegraphicswidth.mm#image_path:adding-field-vectors# center The partial electric field vectors at po P are given by E_A k_C fracQr_AP^fracvecr_APr_APk_C fracQ|vecr_P-vecr_A|^ leftvecr_P-vecr_Aright E_B k_C fracQr_BP^fracvecr_BPr_BPk_C fracQ|vecr_P-vecr_B|^ leftvecr_P-vecr_Bright With vecr_P-vecr_A pmatrix r_P x-r_A x r_P y-r_A y pmatrix pmatrix PxO-rax PyO-rayO pmatrixunitcm pmatrix raPxS raPyP pmatrixunitcm vecr_P-vecr_B pmatrix r_P x-r_B x r_P y-r_B y pmatrix pmatrix PxO-rbx PyO-rbyO pmatrixunitcm pmatrix rbPxS rbPyS pmatrixunitcm and |vecr_P-vecr_A| sqrtraPxS^+raPyP^unitcmraPunitcm |vecr_P-vecr_B| sqrtrbPxS^+rbPyS^unitcmrbPunitcm we find vecE_A kCtimesfracqaraPtimes ^-unitm^timespmatrix raPxS raPySpmatrix times ^-unitm pmatrix EAx EAy pmatrix unitkilonewton/C vecE_B kCtimesfracqbrbPtimes ^-unitm^timespmatrix rbPxS rbPySpmatrix times ^-unitm pmatrix EBx EBy pmatrix unitkilonewton/C The net electric field is the of the partial fields: vecE vecE_A+vecE_B pmatrix EAx EAy pmatrix unitkilonewton/C + pmatrix EBx EBy pmatrix unitkilonewton/C pmatrix Ex Ey pmatrix unitkilonewton/C approx result pmatrix ExP EyP pmatrix unitkilonewton/C
The positions of two positive po charges q_AqaO and q_BqbO are are given by vecr_AraxO|rayOunitcm and vecr_BrbxO|rbyOunitcm respectively. Calculate the electric field vector of their combined electric field at po P with vecr_PPxO|PyOunitcm.
Solution:
The strategy is as follows see figure below: itemize item find the vectors from q_A and q_B to the po P item determine the partial fields vecE_A and vecE_B as vectors using the formula for the field of a po charge item add the partial field vectors itemize center includegraphicswidth.mm#image_path:adding-field-vectors# center The partial electric field vectors at po P are given by E_A k_C fracQr_AP^fracvecr_APr_APk_C fracQ|vecr_P-vecr_A|^ leftvecr_P-vecr_Aright E_B k_C fracQr_BP^fracvecr_BPr_BPk_C fracQ|vecr_P-vecr_B|^ leftvecr_P-vecr_Bright With vecr_P-vecr_A pmatrix r_P x-r_A x r_P y-r_A y pmatrix pmatrix PxO-rax PyO-rayO pmatrixunitcm pmatrix raPxS raPyP pmatrixunitcm vecr_P-vecr_B pmatrix r_P x-r_B x r_P y-r_B y pmatrix pmatrix PxO-rbx PyO-rbyO pmatrixunitcm pmatrix rbPxS rbPyS pmatrixunitcm and |vecr_P-vecr_A| sqrtraPxS^+raPyP^unitcmraPunitcm |vecr_P-vecr_B| sqrtrbPxS^+rbPyS^unitcmrbPunitcm we find vecE_A kCtimesfracqaraPtimes ^-unitm^timespmatrix raPxS raPySpmatrix times ^-unitm pmatrix EAx EAy pmatrix unitkilonewton/C vecE_B kCtimesfracqbrbPtimes ^-unitm^timespmatrix rbPxS rbPySpmatrix times ^-unitm pmatrix EBx EBy pmatrix unitkilonewton/C The net electric field is the of the partial fields: vecE vecE_A+vecE_B pmatrix EAx EAy pmatrix unitkilonewton/C + pmatrix EBx EBy pmatrix unitkilonewton/C pmatrix Ex Ey pmatrix unitkilonewton/C approx result pmatrix ExP EyP pmatrix unitkilonewton/C
Contained in these collections:
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Electric Field (GF) by by
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Electric Field by by

