Two Point Charges
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
Short
Video
\(\LaTeX\)
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Don't forget to subscribe to our channel, like the videos and leave comments!
Exercise:
A po charge + Q is placed at distance d to the left of a po charge -n Q. Determine the pos along the straight line connecting the two charges where the total electric field vanishes.
Solution:
The only possible location for the solution is to the left of +Q since the two partial field vectors vecE_ and vecE_ have to have opposite directions and the same magnitude. With x being the distance from +Q the two partial fields have magnitudes E_+ k_CfracQx^ E_- k_Cfracn Qd+x^ Since they have to be equal E_E_ it follows that k_CfracQx^ k_Cfracn Qd+x^ fracx^ fracnd+x^ d+x^ n x^ d^+ d x + x^ n x^ nm x^- d x - d^ This is a quadratic with solutions x_pm fracdpmsqrtd^+nf d^den fracdpmsqrtd^ +nmdenfracdpm dsqrtnden fracd pmsqrtnden ifthenelsedenX dpmsqrtnfracdpmsqrtnnm The positive solution x_+ifthenelsedenX d+sqrtnd+sqrtn/nm is the one we are looking for. The negative solution x_-ifthenelsedenX d-sqrtnd-sqrtn/nm is between the two charges. At this po the two partial field vectors have the same magnitude but they po in the same direction.
A po charge + Q is placed at distance d to the left of a po charge -n Q. Determine the pos along the straight line connecting the two charges where the total electric field vanishes.
Solution:
The only possible location for the solution is to the left of +Q since the two partial field vectors vecE_ and vecE_ have to have opposite directions and the same magnitude. With x being the distance from +Q the two partial fields have magnitudes E_+ k_CfracQx^ E_- k_Cfracn Qd+x^ Since they have to be equal E_E_ it follows that k_CfracQx^ k_Cfracn Qd+x^ fracx^ fracnd+x^ d+x^ n x^ d^+ d x + x^ n x^ nm x^- d x - d^ This is a quadratic with solutions x_pm fracdpmsqrtd^+nf d^den fracdpmsqrtd^ +nmdenfracdpm dsqrtnden fracd pmsqrtnden ifthenelsedenX dpmsqrtnfracdpmsqrtnnm The positive solution x_+ifthenelsedenX d+sqrtnd+sqrtn/nm is the one we are looking for. The negative solution x_-ifthenelsedenX d-sqrtnd-sqrtn/nm is between the two charges. At this po the two partial field vectors have the same magnitude but they po in the same direction.
Meta Information
Exercise:
A po charge + Q is placed at distance d to the left of a po charge -n Q. Determine the pos along the straight line connecting the two charges where the total electric field vanishes.
Solution:
The only possible location for the solution is to the left of +Q since the two partial field vectors vecE_ and vecE_ have to have opposite directions and the same magnitude. With x being the distance from +Q the two partial fields have magnitudes E_+ k_CfracQx^ E_- k_Cfracn Qd+x^ Since they have to be equal E_E_ it follows that k_CfracQx^ k_Cfracn Qd+x^ fracx^ fracnd+x^ d+x^ n x^ d^+ d x + x^ n x^ nm x^- d x - d^ This is a quadratic with solutions x_pm fracdpmsqrtd^+nf d^den fracdpmsqrtd^ +nmdenfracdpm dsqrtnden fracd pmsqrtnden ifthenelsedenX dpmsqrtnfracdpmsqrtnnm The positive solution x_+ifthenelsedenX d+sqrtnd+sqrtn/nm is the one we are looking for. The negative solution x_-ifthenelsedenX d-sqrtnd-sqrtn/nm is between the two charges. At this po the two partial field vectors have the same magnitude but they po in the same direction.
A po charge + Q is placed at distance d to the left of a po charge -n Q. Determine the pos along the straight line connecting the two charges where the total electric field vanishes.
Solution:
The only possible location for the solution is to the left of +Q since the two partial field vectors vecE_ and vecE_ have to have opposite directions and the same magnitude. With x being the distance from +Q the two partial fields have magnitudes E_+ k_CfracQx^ E_- k_Cfracn Qd+x^ Since they have to be equal E_E_ it follows that k_CfracQx^ k_Cfracn Qd+x^ fracx^ fracnd+x^ d+x^ n x^ d^+ d x + x^ n x^ nm x^- d x - d^ This is a quadratic with solutions x_pm fracdpmsqrtd^+nf d^den fracdpmsqrtd^ +nmdenfracdpm dsqrtnden fracd pmsqrtnden ifthenelsedenX dpmsqrtnfracdpmsqrtnnm The positive solution x_+ifthenelsedenX d+sqrtnd+sqrtn/nm is the one we are looking for. The negative solution x_-ifthenelsedenX d-sqrtnd-sqrtn/nm is between the two charges. At this po the two partial field vectors have the same magnitude but they po in the same direction.
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Electric Field (GF) by by
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Electric Field by by