Horizontal wire -- magnetic field
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
\(\LaTeX\)
Need help? Yes, please!
The following quantities appear in the problem:
elektrische Stromstärke \(I\) / Magnetische Flussdichte \(B\) / Winkel \(\theta\) /
The following formulas must be used to solve the exercise:
\(\cos\alpha = \dfrac{b}{c} \quad \) \(B = \dfrac{\mu_0 I}{2\pi r} \quad \) \(a^2+b^2=c^2 \quad \)
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Exercise:
A very long horizontal cable carries .A of current due to north. What is the resulting magnetic field .in due to west of the wire if the Earth's field there pos north but downward ang below the horizontal and has magnitude microtesla?
Solution:
newqtyI.A newqtyro.in solqtyrron*.m newqtypdegree newqtyBeomicrotesla newqtyBeBeon tesla newqtymuo.newtonpersquareampere % prvminipagecm Geg I I r ro r sscphiI p B_EarthIndex Beo Be % GesMagnetic Flux DensityB siT % View from above: center tikzpicturelatex draw nodebelowS -- ++ coordinate N nodeaboveN; drawvery thick darkgreen- noderightI -- ++.; nodeleft at -. W; noderight at . E; drawdarkgreen snakebrace -- nodebelowr ++-. coordinate Bw; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; draw- orange dashed xshiftmm yshiftmmBw -- ++ noderightsscBh; tikzpicture center View from south: center tikzpicturelatex drawdarkgreen snakebrace -. -- nodebelowr ++-. coordinate Bw; nodedarkgreen at largetimes; drawdarkgreen noderightxshiftmmI circle pt; nodeleft at -. W; noderight at . E; fillorange Bw circle pt; draworang Bw -- ++ nodeabovesscBw; draworang dashed Bw -- ++-. nodebelowsscBperp; nodeorange xshiftmm yshiftmm at Bw largetimes; draworange dashed xshiftmmyshiftmmBw noderight xshiftmmyshiftmmsscBh circle pt; tikzpicture center % The magnetic field due to the wire is solqtyBwfracmu_ Ipi rmuon*In/*pi*rnT al sscBw Bwf fracmuo Ipi r Bw poing upwards. The horizontal component of the resulting field is equal to the horizontal component of the Earth's magnetic field i.e.: solqtyBhB_EarthIndex cossscphiIBen*cosdpnT al sscBh Bhf Be cosp Bh. The vertical component of the resulting field is the Earth's vertical component minus the magnetic field due to the wire i.e.: solqtyBvB_EarthIndex sinsscphiI - fracmu_ Ipi rBen*sindpn-BwnT al sscBV B_perp - sscBw Bvf Be sinp - Bw Bv. Hence the magnitude of the resulting field is according to Pythagoras: solqtyBsqrtB_EarthIndex^ - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^sqrtBhn**+Bvn**T al B sqrtsscBH^ + sscBV^ prv sqrtB_EarthIndex^cossscphiI + B_EarthIndex^sinsscphiI - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^ prv Bf sqrtqtyBh^ + qtyBv^ B. B Bf BII TecB- prvminipage
A very long horizontal cable carries .A of current due to north. What is the resulting magnetic field .in due to west of the wire if the Earth's field there pos north but downward ang below the horizontal and has magnitude microtesla?
Solution:
newqtyI.A newqtyro.in solqtyrron*.m newqtypdegree newqtyBeomicrotesla newqtyBeBeon tesla newqtymuo.newtonpersquareampere % prvminipagecm Geg I I r ro r sscphiI p B_EarthIndex Beo Be % GesMagnetic Flux DensityB siT % View from above: center tikzpicturelatex draw nodebelowS -- ++ coordinate N nodeaboveN; drawvery thick darkgreen- noderightI -- ++.; nodeleft at -. W; noderight at . E; drawdarkgreen snakebrace -- nodebelowr ++-. coordinate Bw; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; draw- orange dashed xshiftmm yshiftmmBw -- ++ noderightsscBh; tikzpicture center View from south: center tikzpicturelatex drawdarkgreen snakebrace -. -- nodebelowr ++-. coordinate Bw; nodedarkgreen at largetimes; drawdarkgreen noderightxshiftmmI circle pt; nodeleft at -. W; noderight at . E; fillorange Bw circle pt; draworang Bw -- ++ nodeabovesscBw; draworang dashed Bw -- ++-. nodebelowsscBperp; nodeorange xshiftmm yshiftmm at Bw largetimes; draworange dashed xshiftmmyshiftmmBw noderight xshiftmmyshiftmmsscBh circle pt; tikzpicture center % The magnetic field due to the wire is solqtyBwfracmu_ Ipi rmuon*In/*pi*rnT al sscBw Bwf fracmuo Ipi r Bw poing upwards. The horizontal component of the resulting field is equal to the horizontal component of the Earth's magnetic field i.e.: solqtyBhB_EarthIndex cossscphiIBen*cosdpnT al sscBh Bhf Be cosp Bh. The vertical component of the resulting field is the Earth's vertical component minus the magnetic field due to the wire i.e.: solqtyBvB_EarthIndex sinsscphiI - fracmu_ Ipi rBen*sindpn-BwnT al sscBV B_perp - sscBw Bvf Be sinp - Bw Bv. Hence the magnitude of the resulting field is according to Pythagoras: solqtyBsqrtB_EarthIndex^ - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^sqrtBhn**+Bvn**T al B sqrtsscBH^ + sscBV^ prv sqrtB_EarthIndex^cossscphiI + B_EarthIndex^sinsscphiI - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^ prv Bf sqrtqtyBh^ + qtyBv^ B. B Bf BII TecB- prvminipage
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Exercise:
A very long horizontal cable carries .A of current due to north. What is the resulting magnetic field .in due to west of the wire if the Earth's field there pos north but downward ang below the horizontal and has magnitude microtesla?
Solution:
newqtyI.A newqtyro.in solqtyrron*.m newqtypdegree newqtyBeomicrotesla newqtyBeBeon tesla newqtymuo.newtonpersquareampere % prvminipagecm Geg I I r ro r sscphiI p B_EarthIndex Beo Be % GesMagnetic Flux DensityB siT % View from above: center tikzpicturelatex draw nodebelowS -- ++ coordinate N nodeaboveN; drawvery thick darkgreen- noderightI -- ++.; nodeleft at -. W; noderight at . E; drawdarkgreen snakebrace -- nodebelowr ++-. coordinate Bw; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; draw- orange dashed xshiftmm yshiftmmBw -- ++ noderightsscBh; tikzpicture center View from south: center tikzpicturelatex drawdarkgreen snakebrace -. -- nodebelowr ++-. coordinate Bw; nodedarkgreen at largetimes; drawdarkgreen noderightxshiftmmI circle pt; nodeleft at -. W; noderight at . E; fillorange Bw circle pt; draworang Bw -- ++ nodeabovesscBw; draworang dashed Bw -- ++-. nodebelowsscBperp; nodeorange xshiftmm yshiftmm at Bw largetimes; draworange dashed xshiftmmyshiftmmBw noderight xshiftmmyshiftmmsscBh circle pt; tikzpicture center % The magnetic field due to the wire is solqtyBwfracmu_ Ipi rmuon*In/*pi*rnT al sscBw Bwf fracmuo Ipi r Bw poing upwards. The horizontal component of the resulting field is equal to the horizontal component of the Earth's magnetic field i.e.: solqtyBhB_EarthIndex cossscphiIBen*cosdpnT al sscBh Bhf Be cosp Bh. The vertical component of the resulting field is the Earth's vertical component minus the magnetic field due to the wire i.e.: solqtyBvB_EarthIndex sinsscphiI - fracmu_ Ipi rBen*sindpn-BwnT al sscBV B_perp - sscBw Bvf Be sinp - Bw Bv. Hence the magnitude of the resulting field is according to Pythagoras: solqtyBsqrtB_EarthIndex^ - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^sqrtBhn**+Bvn**T al B sqrtsscBH^ + sscBV^ prv sqrtB_EarthIndex^cossscphiI + B_EarthIndex^sinsscphiI - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^ prv Bf sqrtqtyBh^ + qtyBv^ B. B Bf BII TecB- prvminipage
A very long horizontal cable carries .A of current due to north. What is the resulting magnetic field .in due to west of the wire if the Earth's field there pos north but downward ang below the horizontal and has magnitude microtesla?
Solution:
newqtyI.A newqtyro.in solqtyrron*.m newqtypdegree newqtyBeomicrotesla newqtyBeBeon tesla newqtymuo.newtonpersquareampere % prvminipagecm Geg I I r ro r sscphiI p B_EarthIndex Beo Be % GesMagnetic Flux DensityB siT % View from above: center tikzpicturelatex draw nodebelowS -- ++ coordinate N nodeaboveN; drawvery thick darkgreen- noderightI -- ++.; nodeleft at -. W; noderight at . E; drawdarkgreen snakebrace -- nodebelowr ++-. coordinate Bw; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; fillorange yshiftmmBw nodeleft xshift-mmsscBw circle pt; draworange yshiftmmBw circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; nodeorange yshiftmm at Bw largetimes; draworange dashed yshiftmmBw nodeleft xshift-mmsscBperp circle pt; draw- orange dashed xshiftmm yshiftmmBw -- ++ noderightsscBh; tikzpicture center View from south: center tikzpicturelatex drawdarkgreen snakebrace -. -- nodebelowr ++-. coordinate Bw; nodedarkgreen at largetimes; drawdarkgreen noderightxshiftmmI circle pt; nodeleft at -. W; noderight at . E; fillorange Bw circle pt; draworang Bw -- ++ nodeabovesscBw; draworang dashed Bw -- ++-. nodebelowsscBperp; nodeorange xshiftmm yshiftmm at Bw largetimes; draworange dashed xshiftmmyshiftmmBw noderight xshiftmmyshiftmmsscBh circle pt; tikzpicture center % The magnetic field due to the wire is solqtyBwfracmu_ Ipi rmuon*In/*pi*rnT al sscBw Bwf fracmuo Ipi r Bw poing upwards. The horizontal component of the resulting field is equal to the horizontal component of the Earth's magnetic field i.e.: solqtyBhB_EarthIndex cossscphiIBen*cosdpnT al sscBh Bhf Be cosp Bh. The vertical component of the resulting field is the Earth's vertical component minus the magnetic field due to the wire i.e.: solqtyBvB_EarthIndex sinsscphiI - fracmu_ Ipi rBen*sindpn-BwnT al sscBV B_perp - sscBw Bvf Be sinp - Bw Bv. Hence the magnitude of the resulting field is according to Pythagoras: solqtyBsqrtB_EarthIndex^ - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^sqrtBhn**+Bvn**T al B sqrtsscBH^ + sscBV^ prv sqrtB_EarthIndex^cossscphiI + B_EarthIndex^sinsscphiI - fracmu_IB_EarthIndexsinsscphiIpi r + fracmu_^I^pi^ r^ prv Bf sqrtqtyBh^ + qtyBv^ B. B Bf BII TecB- prvminipage
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