(function () { function textOf(el) { return (el && el.textContent || "").replace(/\s+/g, " ").trim(); } function resolveItemUrl() { var match = window.location.search.match(/[?&]item=(\d+)/); if (!match) { return null; } return window.location.origin + "/a-" + match[1] + "/"; } function loadAccordion() { var url = resolveItemUrl(); if (!url) { return Promise.resolve(null); } return new Promise(function (resolve, reject) { var xhr = new XMLHttpRequest(); xhr.open("GET", url, true); xhr.onload = function () { if (xhr.status < 200 || xhr.status >= 400) { reject(new Error("item page " + xhr.status)); return; } var doc = new DOMParser().parseFromString(xhr.responseText, "text/html"); resolve(doc.querySelector(".phywe-item-accordion")); }; xhr.onerror = function () { reject(new Error("item page network error")); }; xhr.send(); }); } function parseItemBlocks(scope, withQuantity) { if (!scope) { return []; } var rows = scope.querySelectorAll(".itemslist .row.itemblocks"); var items = []; for (var i = 0; i < rows.length; i++) { var cols = rows[i].children; if (!cols.length) { continue; } var nameLink = cols[0].querySelector("a"); var numberLink = cols[1] ? cols[1].querySelector("a") : null; var item = { name: textOf(nameLink || cols[0]), mappedTo: textOf(numberLink) }; if (withQuantity && cols[2]) { var qty = parseInt(textOf(cols[2]).replace(/[^\d]/g, ""), 10); item.quantity = isNaN(qty) ? textOf(cols[2]) : String(qty); } if (item.name) { items.push(item); } } return items; } function fillTable(tableId, items, withQuantity) { var table = document.getElementById(tableId); if (!table || !items.length) { return; } var tbody = table.querySelector("tbody"); for (var i = 0; i < items.length; i++) { var tr = document.createElement("tr"); var nameTd = document.createElement("td"); nameTd.style.width = "80%"; nameTd.textContent = items[i].name; tr.appendChild(nameTd); var numberTd = document.createElement("td"); numberTd.textContent = items[i].mappedTo; tr.appendChild(numberTd); if (withQuantity) { var qtyTd = document.createElement("td"); qtyTd.textContent = items[i].quantity || ""; tr.appendChild(qtyTd); } tbody.appendChild(tr); } var wrapper = table.parentElement; while (wrapper && wrapper.className.indexOf("printtablediv") === -1) { wrapper = wrapper.parentElement; } if (wrapper) { wrapper.style.display = ""; } } function stepTitle(stepEl) { if (!stepEl) { return ""; } var titleEl = stepEl.querySelector(".card-header button div") || stepEl.querySelector(".card-header button"); return textOf(titleEl); } function setHeadline(tableId, title) { var headline = document.querySelector("#" + tableId + " .printtableheadline"); if (headline && title) { headline.textContent = title; } } function parseMedia(scope) { if (!scope) { return []; } var rows = scope.querySelectorAll(".itemslist .row.itemblocks"); var items = []; for (var i = 0; i < rows.length; i++) { var cols = rows[i].children; if (!cols.length) { continue; } var nameLink = cols[0].querySelector("a"); var fileLink = cols[1] ? cols[1].querySelector("a") : null; var item = { name: textOf(nameLink || cols[0]), mappedTo: textOf(fileLink || cols[1]), quantity: cols[2] ? textOf(cols[2]) : "" }; if (item.name) { items.push(item); } } return items; } function fillFromAccordion(accordion) { if (!accordion) { return; } var versucheStep = accordion.querySelector('[data-step="versuche"]'); var versuche = parseItemBlocks(versucheStep, false); setHeadline("print-versuche", stepTitle(versucheStep)); fillTable("print-versuche", versuche, false); var lieferumfangStep = accordion.querySelector('[data-step="lieferumfang"]'); var lieferumfang = parseItemBlocks(lieferumfangStep, true); fillTable("print-lieferumfang", lieferumfang, true); var zubehoer = accordion.querySelector('[data-step="zubehoer"]'); var sections = zubehoer ? zubehoer.querySelectorAll(".card-body") : []; var notwendig = []; var empfohlen = []; for (var i = 0; i < sections.length; i++) { var items = parseItemBlocks(sections[i], false); if (sections[i].querySelector(".text-red, .icon-warning-black")) { notwendig = items; } else if (sections[i].querySelector(".text-green, .icon-Mehrwert_black")) { empfohlen = items; } } fillTable("print-zubehoer-notwendig", notwendig, false); fillTable("print-zubehoer-empfohlen", empfohlen, false); var mediaStep = accordion.querySelector('[data-step="media"]'); var media = parseMedia(mediaStep); setHeadline("print-media", stepTitle(mediaStep)); fillTable("print-media", media, true); } function start() { var itemUrl = resolveItemUrl(); if (!itemUrl) { setTimeout(function () { window.print(); }, 2000); return; } loadAccordion() .then(function (accordion) { fillFromAccordion(accordion); }) .catch(function (err) { if (window.console && console.warn) { console.warn("Accordion konnte nicht geladen werden:", resolveItemUrl(), err); } }) .then(function () { setTimeout(function () { window.print(); }, 500); }); } if (document.readyState === "loading") { document.addEventListener("DOMContentLoaded", start); } else { start(); } })();
 

Technical data


The transistor as a voltage amplifier

Article no: P1378500
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Principle

This experiment serves as an introduction to the application of transistors for amplifying alternating voltage.
The stray field produced by the transformer of the power supply unit induces a small alternating voltage in the coil. It is so minimal that it can not be sufficiently detected directly with the headphones. To attain the necessary voltage amplification, the alternating voltage is superimposed on a base voltage produced by a voltage divider. This alternating voltage controls the collector current periodically around the average value set by the bias voltage. The fluctuations in the collector current produce voltage fluctuations in the headphones, evidenced by a humming noise.

This experiment also serves as an introduction to the much discussed "electromagnetic pollution" issue. It proves that electrical devices produce magnetic fields in their surroundings when being in operation.

Benefits

  • No additional cable connections between the building blocks needed - clear arragned and quick setup
  • Contact saftey due to puzzle blocks system
  • Corrosion-free gold plated contacts
  • Doubled earning sucess: Electric circuit diagram on top, real components can be seen unterside

Tasks

How can electromagnetic pollution be detected?

Try to amplify the small alternating voltages induced by alternating magnetic fields of the power supply unit in a coil so that they can be detected on headphones.

 


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