// Numbas version: exam_results_page_options
{"name": "Coulomb's Law for a pair of charges", "extensions": [], "custom_part_types": [], "resources": [["question-resources/CoulombForce1.png", "/srv/numbas/media/question-resources/CoulombForce1.png"], ["question-resources/CoulombForce2.png", "/srv/numbas/media/question-resources/CoulombForce2.png"], ["question-resources/CoulombForce3.png", "/srv/numbas/media/question-resources/CoulombForce3.png"], ["question-resources/CoulombForce4.png", "/srv/numbas/media/question-resources/CoulombForce4.png"]], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "Coulomb's Law for a pair of charges", "tags": ["coulomb", "elec", "field", "force", "mid1718"], "metadata": {"description": "Concepts and calculation involved in the use of Coulomb's Law for both the field and the force, including units and directions.", "licence": "All rights reserved"}, "statement": "<p>This question assesses understanding of the names and units of symbols in the Coulomb equation, the ability to perform calculation of quantities and to evaluate of force directions.&nbsp;&nbsp;</p>\n<p>When providing numerical answers you may express them using scientific notation.&nbsp; Express values to four significant figures and use the values of physical constants as provided in the course notes.</p>", "advice": "<p>The Coulomb field is for a point charge (the equation does not generally apply to all charge arrangements):</p>\n<table>\n<tbody>\n<tr>\n<td>Symbol</td>\n<td>Description</td>\n<td>Units</td>\n</tr>\n<tr>\n<td>$E$</td>\n<td>Electric field strength</td>\n<td>V/m (or N/C)</td>\n</tr>\n<tr>\n<td>$q$</td>\n<td>Point charge</td>\n<td>C</td>\n</tr>\n<tr>\n<td>$\\varepsilon_0$</td>\n<td>Permittivity of free space</td>\n<td>F/m</td>\n</tr>\n<tr>\n<td>$\\varepsilon_r$</td>\n<td>Relative permittivity of medium betweem the point charge and where the field is being established</td>\n<td>none</td>\n</tr>\n<tr>\n<td>$r$</td>\n<td>Distance from the point charge - it's definitely not a radius!</td>\n<td>m</td>\n</tr>\n<tr>\n<td>$\\hat{r}$</td>\n<td>This is the unit radial vector.&nbsp; It is not a displacement (which would have units of m).</td>\n<td>none</td>\n</tr>\n</tbody>\n</table>\n<p>In the calculation of the magnitude of the electric field strength, care has to be taken to correctly account for units.</p>\n<p>From the electric field, a force can be obtained using $F=qE$.&nbsp; For this problem the field has already been obtained, and all that's required is to multiply this by the magnitude of the second point charge.</p>\n<p>Since the charges are opposite in sign, they attract.</p>", "rulesets": {}, "extensions": [], "variables": {"q2": {"name": "q2", "group": "Ungrouped variables", "definition": "q2mu/10^6", "description": "<p>Second point charge in C.</p>", "templateType": "anything"}, "q1": {"name": "q1", "group": "Ungrouped variables", "definition": "q1mu/10^6", "description": "<p>Point charge in C.</p>", "templateType": "anything"}, "efield": {"name": "efield", "group": "Ungrouped variables", "definition": "q1/(4 pi eps0 r^2)", "description": "<p>Electric field at the distant point in N/C.</p>", "templateType": "anything"}, "q2mu": {"name": "q2mu", "group": "Ungrouped variables", "definition": "random(1..20 except q1mu*10)*-0.1", "description": "<p>Charge on the second point charge in muC.</p>", "templateType": "anything"}, "rmm": {"name": "rmm", "group": "Ungrouped variables", "definition": "random(1..20)*0.1", "description": "<p>Radial distance from the point charge, mm.</p>", "templateType": "anything"}, "r": {"name": "r", "group": "Ungrouped variables", "definition": "rmm/1000", "description": "<p>Radial distance from the point charge, m.</p>", "templateType": "anything"}, "force": {"name": "force", "group": "Ungrouped variables", "definition": "-efield*q2", "description": "<p>Magnitude of force on second point charge, N.</p>", "templateType": "anything"}, "eps0": {"name": "eps0", "group": "Ungrouped variables", "definition": "8.854*10^-12", "description": "<p>Permittivity of free space, F/m.</p>", "templateType": "anything"}, "q1mu": {"name": "q1mu", "group": "Ungrouped variables", "definition": "random(1..20 except rmm*10)*0.1", "description": "<p>Point charge in micro-C.</p>", "templateType": "anything"}}, "variablesTest": {"condition": "", "maxRuns": 100}, "ungrouped_variables": ["efield", "eps0", "force", "q1", "q1mu", "q2", "q2mu", "r", "rmm"], "variable_groups": [], "functions": {}, "preamble": {"js": "", "css": ""}, "parts": [{"type": "information", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>Coulomb's Law is embodied in the equation&nbsp;</p>\n<p style=\"text-align: center;\">$\\displaystyle \\vec{E}= {q\\over 4 \\pi \\varepsilon_0 \\varepsilon_r r^2}\\hat{r}$.</p>"}, {"type": "gapfill", "useCustomName": true, "customName": "Symbols, their meanings and their units", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p style=\"text-align: center;\">$\\vec{E}$ is&nbsp;[[0]] with units&nbsp;[[1]]</p>\n<p style=\"text-align: center;\">$q$ is&nbsp;[[2]] with units&nbsp;[[3]]</p>\n<p style=\"text-align: center;\">$\\varepsilon_0$ is&nbsp;[[4]] with units&nbsp;[[5]]</p>\n<p style=\"text-align: center;\">$\\varepsilon_r$ is&nbsp;[[6]] with units&nbsp;[[7]]</p>\n<p style=\"text-align: center;\">$r$ is&nbsp;[[8]] with units&nbsp;[[9]]</p>\n<p style=\"text-align: center;\">$\\hat{r}$ is&nbsp;[[10]] with units&nbsp;[[11]]</p>", "gaps": [{"type": "1_n_2", "useCustomName": true, "customName": "DE", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["electric field strength", "electric flux", "charge", "point charge", "permeability", "permeability of free space", "permeability of the material", "relative permeability of the material", "permittivity of the material", "permittivity of free space", "relative permittivity of the material", "radius", "distance from the point charge", "displacement vector", "unit displacement vector", "unit&nbsp;radial vector"], "matrix": ["1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "UE", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["V/m", "N/C", "C", "F/m", "none", "m", "J", "A", "V", "N", "F", "K", "eV", "Pa", "kg", "Hz"], "matrix": ["1", "1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Dq", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["electric field strength", "electric flux", "charge", "point charge", "permeability", "permeability of free space", "permeability of the material", "relative permeability of the material", "permittivity of the material", "permittivity of free space", "relative permittivity of the material", "radius", "distance from the point charge", "displacement vector", "unit displacement vector", "unit&nbsp;radial vector"], "matrix": [0, 0, 0, "1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "No - it's a point charge!", "", "", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Uq", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["V/m", "N/C", "C", "F/m", "none", "m", "J", "A", "V", "N", "F", "K", "eV", "Pa", "kg", "Hz"], "matrix": [0, 0, "1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Deps0", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["electric field strength", "electric flux", "charge", "point charge", "permeability", "permeability of free space", "permeability of the material", "relative permeability of the material", "permittivity of the material", "permittivity of free space", "relative permittivity of the material", "radius", "distance from the point charge", "displacement vector", "unit displacement vector", "unit&nbsp;radial vector"], "matrix": [0, 0, 0, 0, 0, "0", 0, 0, 0, "1", 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "No - permittivity", "No - permittivity", "No - permittivity", "No - permittivity", "No - the subscript implies free space!", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Ueps0", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["V/m", "N/C", "C", "F/m", "none", "m", "J", "A", "V", "N", "F", "K", "eV", "Pa", "kg", "Hz"], "matrix": [0, 0, 0, "1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Depsr", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["electric field strength", "electric flux", "charge", "point charge", "permeability", "permeability of free space", "permeability of the material", "relative permeability of the material", "permittivity of the material", "permittivity of free space", "relative permittivity of the material", "radius", "distance from the point charge", "displacement vector", "unit displacement vector", "unit&nbsp;radial vector"], "matrix": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1", 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "No - permittivity", "No - permittivity", "No - permittivity", "No - permittivity", "No - it's only relative", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Uepsr", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["V/m", "N/C", "C", "F/m", "none", "m", "J", "A", "V", "N", "F", "K", "eV", "Pa", "kg", "Hz"], "matrix": [0, 0, 0, 0, "1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "Yes - it simply scales $\\varepsilon_0$", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Dr", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["electric field strength", "electric flux", "charge", "point charge", "permeability", "permeability of free space", "permeability of the material", "relative permeability of the material", "permittivity of the material", "permittivity of free space", "relative permittivity of the material", "radius", "distance from the point charge", "displacement vector", "unit displacement vector", "unit&nbsp;radial vector"], "matrix": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "1", 0, 0, 0], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "Of what?", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Ur", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["V/m", "N/C", "C", "F/m", "none", "m", "J", "A", "V", "N", "F", "K", "eV", "Pa", "kg", "Hz"], "matrix": [0, 0, 0, 0, 0, "1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Drhat", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["electric field strength", "electric flux", "charge", "point charge", "permeability", "permeability of free space", "permeability of the material", "relative permeability of the material", "permittivity of the material", "permittivity of free space", "relative permittivity of the material", "radius", "distance from the point charge", "displacement vector", "unit displacement vector", "unit&nbsp;radial vector"], "matrix": [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, "0", "1"], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""]}, {"type": "1_n_2", "useCustomName": true, "customName": "Urhat", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["V/m", "N/C", "C", "F/m", "none", "m", "J", "A", "V", "N", "F", "K", "eV", "Pa", "kg", "Hz"], "matrix": [0, 0, 0, 0, "1", 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], "distractors": ["", "", "", "", "", "", "", "", "", "", "", "", "", "", "", ""]}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": true, "customName": "E-field value", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>Calculate the magnitude of the electric field {rmm}&nbsp;mm from a {q1mu}&nbsp;&mu;C point charge in vacuum.</p>\n<p style=\"text-align: center;\">$|\\vec{E}|=$ [[0]]&nbsp;[[1]]</p>", "gaps": [{"type": "numberentry", "useCustomName": true, "customName": "E value", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "efield*0.995", "maxValue": "efield*1.005", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "4", "precisionPartialCredit": 0, "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": false, "notationStyles": ["plain", "en", "si-en", "scientific"], "correctAnswerStyle": "plain"}, {"type": "1_n_2", "useCustomName": true, "customName": "units", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["N/C", "V/m", "A/m", "J/m", "C/s", "F/m"], "matrix": ["1", "1", 0, 0, 0, 0], "distractors": ["", "", "", "", "", ""]}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": true, "customName": "Force", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>What is the equation for the force that a second point charge, $q_2$ (q_2) would experience is placed in the electric field $E_1$ (E_1) due to the first point charge?</p>\n<p style=\"text-align: center;\">$F=$[[0]]</p>", "gaps": [{"type": "jme", "useCustomName": true, "customName": "formula", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "answer": "q_2 E_1", "showPreview": true, "checkingType": "absdiff", "checkingAccuracy": 0.001, "failureRate": 1, "vsetRangePoints": 5, "vsetRange": [0, 1], "checkVariableNames": true, "singleLetterVariables": true, "allowUnknownFunctions": true, "implicitFunctionComposition": false, "valuegenerators": [{"name": "e_1", "value": ""}, {"name": "q_2", "value": ""}]}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": true, "customName": "Force value", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [{"variable": "efield", "part": "p2g0", "must_go_first": false}], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>Calculate the magnitude of the&nbsp;force a {q2mu}&nbsp;&mu;C point charge would experience if placed {rmm}&nbsp;mm from a {q1mu}&nbsp;&mu;C point charge in vacuum.</p>\n<p style=\"text-align: center;\">$|\\vec{F}|=$ [[0]]&nbsp;[[1]]</p>", "gaps": [{"type": "numberentry", "useCustomName": true, "customName": "F Value", "marks": 1, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [{"variable": "efield", "part": "p2g0", "must_go_first": false}], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minValue": "force*0.995", "maxValue": "force*1.005", "correctAnswerFraction": false, "allowFractions": false, "mustBeReduced": false, "mustBeReducedPC": 0, "precisionType": "sigfig", "precision": "4", "precisionPartialCredit": 0, "precisionMessage": "You have not given your answer to the correct precision.", "strictPrecision": false, "showPrecisionHint": false, "notationStyles": ["plain", "en", "si-en", "scientific"], "correctAnswerStyle": "plain"}, {"type": "1_n_2", "useCustomName": true, "customName": "units", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "dropdownlist", "displayColumns": 0, "showCellAnswerState": true, "choices": ["N", "V", "A", "J", "C", "F"], "matrix": ["1", "0", 0, 0, 0, 0], "distractors": ["", "", "", "", "", ""]}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": true, "customName": "Direction", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "<p>What are the directions of the forces experienced by both charges in this case (the direction for the vector with a positive magnitude)?</p>\n<p>[[0]]</p>", "gaps": [{"type": "1_n_2", "useCustomName": true, "customName": "Direction", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "minMarks": 0, "maxMarks": 0, "shuffleChoices": true, "displayType": "radiogroup", "displayColumns": "4", "showCellAnswerState": true, "choices": ["<img src=\"resources/question-resources/CoulombForce1.png\"/>", "<img src=\"resources/question-resources/CoulombForce2.png\"/>", "<img src=\"resources/question-resources/CoulombForce3.png\"/>", "<img src=\"resources/question-resources/CoulombForce4.png\"/>"], "matrix": ["1", 0, 0, 0], "distractors": ["Opposite charges attract!", "Opposite charges attract!", "Opposite charges attract!", "Opposite charges attract!"]}], "sortAnswers": false}], "partsMode": "all", "maxMarks": 0, "objectives": [], "penalties": [], "objectiveVisibility": "always", "penaltyVisibility": "always", "contributors": [{"name": "Jon Goss", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/3925/"}]}]}], "contributors": [{"name": "Jon Goss", "profile_url": "https://numbas.mathcentre.ac.uk/accounts/profile/3925/"}]}