added RC circuit class with low-pass filter calculation.

Author: Mark Hatchell

src/RC-Circuit.js

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+'use strict';
+
+/**
+ * TankCircuit is a class with methods that can be used without initializing.
+ *
+ * Its methods provide calculations for a Tank Circuit (LC), (Inductor and Capacitor) resonant circuit.
+ *
+ * @example
+ *
+ * RCCircuit.lowPassFilter(1000, 1 / 100000000);
+ *
+ */
+class RCCircuit {
+
+  /**
+   *
+   * Take a value of resistance in ohms and value of capacitance in farads and calculates the
+   * cut off frequency of a low-pass circuit. The return value is in hertz.
+   *
+   * @param {number} resistance
+   * @param {number} capacitance
+   * @returns {number}
+   */
+  static lowPassFilter(resistance, capacitance) {
+    return 1 / (2 * Math.PI * resistance * capacitance);
+  }
+
+
+}
+
+export default RCCircuit;

src/RC-Circuit.test.js

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+const RCCircuit = require('./RC-Circuit');
+
+
+describe('TankCircuit', () => {
+
+  test('if resistance in ohms is 1000 and capacitance in farads is .00000001 then cut-off frequency should be 15915.494309189537', () => {
+    const resistance  = 1000;
+    const capacitance = .00000001;
+
+    expect(RCCircuit.lowPassFilter(resistance, capacitance)).toEqual(15915.494309189537)
+  });
+
+
+});