Initial commit

README.md

@@ -1,3 +1,6 @@
-# flutter_demo_energy
+# Beispiel: Energieberechnung & Tests
+
+Aktuell enthält das Repo nur die Business-Logik und die Tests der Energy-App.
+Dieser Code ist unabhängig von Flutter. Die Tests können daher sowohl mit
+`flutter test` als auch `dart test` ausgeführt werden.
 
-Flutter Beispiel Energie-Berechung

analysis_options.yaml

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+# This file configures the analyzer, which statically analyzes Dart code to
+# check for errors, warnings, and lints.
+#
+# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
+# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
+# invoked from the command line by running `flutter analyze`.
+
+# The following line activates a set of recommended lints for Flutter apps,
+# packages, and plugins designed to encourage good coding practices.
+include: package:flutter_lints/flutter.yaml
+
+linter:
+  # The lint rules applied to this project can be customized in the
+  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
+  # included above or to enable additional rules. A list of all available lints
+  # and their documentation is published at
+  # https://dart-lang.github.io/linter/lints/index.html.
+  #
+  # Instead of disabling a lint rule for the entire project in the
+  # section below, it can also be suppressed for a single line of code
+  # or a specific dart file by using the `// ignore: name_of_lint` and
+  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
+  # producing the lint.
+  rules:
+    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
+    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
+
+# Additional information about this file can be found at
+# https://dart.dev/guides/language/analysis-options

lib/models/energy.dart

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+/// free fall acceleration in m/s²
+const double g = 9.81;
+
+///
+/// Potential Energy = [mass] * [height] * g
+/// with [mass] in kg, [height] in m and result in m²kg/s² = Joule
+double potential(double mass, double height) {
+  return mass * height * g;
+}
+
+double freedPotential(double mass, double hStart, double hEnd) {
+  return potential(mass, hStart) - potential(mass, hEnd);
+}
+///
+/// Kinetic energy = 0.5 [mass] * [velocity] * [velocity]
+/// with [mass] in kg and velocity in m/s and result in m²kg/s² = Joule
+double kinetic(double mass, double velocity) {
+  return mass * velocity * velocity / 2;
+}
+
+double freedKinetic(double mass, double vStart, double vEnd) {
+  return kinetic(mass, vStart) - kinetic(mass, vEnd);
+}
+
+///
+/// Amount of freed energy when an object changes its height from [hStart] m to [hEnd] m
+/// and changes its velocity from [vStart] m/s² to [vEnd] m/s².
+double freedEnergy(double mass, double hStart, double hEnd, double vStart, double vEnd) {
+  return freedPotential(mass, hStart, hEnd) + freedKinetic(mass, vStart, vEnd);
+}

lib/models/heat_capacity.dart

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+/// energyNeededToHeatAParticularMaterial = tempDiff * specificHeatCapacity (measued in J/kg)
+/// we have some amount of energy e
+/// e / energyNeededToHeatAParticularMaterial => amount of material which can be heated (in kg)
+/// for H2H: 1 l = 1 kg
+double _kg(double energy, double specHeatCapacity, double tempDiff) {
+  return energy / (tempDiff * specHeatCapacity);
+}
+
+
+/// Notes
+/// Eine PKW-Bremscheibe ca. 6.5kg
+/// LKW Actros: 34kg
+/// Calculates the amount of water in Liter that can be heated
+/// from 20°C to 100°C with the given [engergy] in Joule.
+///
+double literWaterThatCanBeBoiled(double energy) {
+  const double specHeatCapaH2O = 4180; // J(kg*K)
+  const double tempDiffH20 = 100 - 20; // K
+  return _kg(energy, specHeatCapaH2O, tempDiffH20);
+}
+
+///
+/// Calculates the amount of iron in kg that can be heated
+/// from 20°C to ???°C with the given [engergy] in Joule.
+///
+double kgIronThatCanBeHeatetUntilRed(double energy) {
+  const double specHeatCapaIron = 500; // J/(kg*K)
+  const double tempDiffIron = 700 - 20; // K
+  return _kg(energy, specHeatCapaIron, tempDiffIron);
+}
+

lib/models/velocity.dart

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+const _factor = 3.6;
+toKmPerHour(double mPerSecond) => mPerSecond * _factor;
+tomPerSecond(double kmPerHour) => kmPerHour / _factor;

pubspec.yaml

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+name: energy
+description: Demo Application
+
+publish_to: 'none' # Remove this line if you wish to publish to pub.dev
+
+version: 1.0.0+1
+
+environment:
+  sdk: ">=2.18.0 <3.0.0"
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+dev_dependencies:
+  test:
+
+  flutter_lints: ^2.0.1
+

test/energy_test.dart

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+import 'package:energy/models/energy.dart';
+import 'package:test/test.dart';
+
+void main() {
+  const double oneTon = 1000.0; // kg
+  const double tenToStop = 50000.0; // J
+  const double oneTonTenMetersDown = 98100.0; // J
+
+  group('energy', () {
+    test('none', () {
+      expect(freedEnergy(oneTon, 0, 0, 0, 0), 0);
+      expect(freedEnergy(oneTon, 0, 0, 20, 20), 0);
+    });
+    group('potential', () {
+      test('10 m down', () {
+        expect(freedEnergy(oneTon, 10, 0, 0, 0), oneTonTenMetersDown);
+        expect(freedPotential(oneTon, 10, 0), oneTonTenMetersDown);
+      });
+      test('10 m up', () {
+        expect(freedEnergy(oneTon, 0, 10, 0, 0), -oneTonTenMetersDown);
+        expect(freedPotential(oneTon, 0, 10), -oneTonTenMetersDown);
+      });
+      test('20 m down', () {
+        expect(freedEnergy(oneTon, 2 * 10, 0, 0, 0), 2 * oneTonTenMetersDown);
+        expect(potential(oneTon, 2 * 10), 2 * oneTonTenMetersDown);
+      });
+    });
+
+    group('kinetic', () {
+      test('10 to 0', () {
+        expect(freedEnergy(oneTon, 0, 0, 10, 0), tenToStop);
+        expect(freedKinetic(oneTon, 10, 0), tenToStop);
+      });
+      test('0 to 10', () {
+        expect(freedEnergy(oneTon, 0, 0, 0, 10), -tenToStop);
+        expect(freedKinetic(oneTon, 0, 10), -tenToStop);
+      });
+      test('20 to 0', () {
+        expect(freedEnergy(oneTon, 0, 0, 20, 0), 4 * tenToStop);
+        expect(freedKinetic(oneTon, 20, 0), 4 * tenToStop);
+      });
+    });
+
+    group('sum', () {
+      test('10 down & 10 to 0', () {
+        expect(
+            freedEnergy(oneTon, 10, 0, 10, 0), oneTonTenMetersDown + tenToStop);
+      });
+      test('10 up & 0 to 10', () {
+        expect(
+            freedEnergy(oneTon, 0, 10, 0, 10), -(tenToStop + oneTonTenMetersDown));
+      });
+
+      test('10 down & 0 to 10', () {
+        expect(
+            freedEnergy(oneTon, 10, 0, 0, 10), oneTonTenMetersDown - tenToStop);
+      });
+      test('10 up & 10 to 0', () {
+        expect(
+            freedEnergy(oneTon, 0, 10, 10, 0), tenToStop - oneTonTenMetersDown);
+      });
+    });
+  });
+}

test/heat_capacity_test.dart

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+import 'package:energy/models/heat_capacity.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('Joule to', () {
+    test('red heat 1 kg Iron', () {
+      expect(kgIronThatCanBeHeatetUntilRed(340000), 1);
+    });
+    test('boil 1 l Water', () {
+      expect(literWaterThatCanBeBoiled(334400), 1);
+    });});
+}