What is Resistance? (2024)

Resistance is a measure of the opposition to current flow in an electrical circuit.

Resistance is measured in ohms, symbolized by the Greek letter omega (Ω). Ohms are named after Georg Simon Ohm (1784-1854), a German physicist who studied the relationship between voltage, current and resistance. He is credited for formulating Ohm's Law.

All materials resist current flow to some degree. They fall into one of two broad categories:

Conductors: Materials that offer very little resistance where electrons can move easily. Examples: silver, copper, gold and aluminum.
Insulators: Materials that present high resistance and restrict the flow of electrons. Examples: Rubber, paper, glass, wood and plastic.

Resistance measurements are normally taken to indicate the condition of a component or a circuit.

The higher the resistance, the lower the current flow. If abnormally high, one possible cause (among many) could be damaged conductors due to burning or corrosion. All conductors give off some degree of heat, so overheating is an issue often associated with resistance.
The lower the resistance, the higher the current flow. Possible causes: insulators damaged by moisture or overheating.

Many components, such as heating elements and resistors, have a fixed-resistance value. These values are often printed on the components' nameplates or in manuals for reference.

When a tolerance is indicated, the measured resistance value should be within the specified resistance range. Any significant change in a fixed-resistance value usually indicates a problem.

"Resistance" may sound negative, but in electricity it can be used beneficially.

Examples: Current must struggle to flow through the small coils of a toaster, enough to generate heat that browns bread. Old-style incandescent light bulbs force current to flow through filaments so thin that light is generated.

Resistance cannot be measured in an operating circuit. Accordingly, troubleshooting technicians often determine resistance by taking voltage and current measurements and applying Ohm's Law:

E = I x R

That is, volts = amps x ohms. R stands for resistance in this formula. If resistance is unknown, the formula can be converted to R = E/I (ohms = volts divided by amps).

Examples: In an electric heater circuit, as portrayed in the two illustrations below, resistance is determined by measuring circuit voltage and current, then applying Ohm's Law.

In the first example, total normal circuit resistance, a known reference value, is 60 Ω (240 ÷ 4 = 60 Ω). The 60 Ω resistance can help determine the condition of a circuit.

In the second example, if circuit current is 3 amps instead of 4, circuit resistance has increased from 60 Ω to 80 Ω (240 ÷ 3 = 80 Ω). The 20 Ω gain in total resistance could be caused by a loose or dirty connection or an open-coil section. Open-coil sections increase the total circuit resistance, which decreased current.

Reference: Digital Multimeter Principles by Glen A. Mazur, American Technical Publishers.

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How can I help you today?

" + "

I want to learn more about a product

" + "

I want to purchase a product

" + "

I am looking for product support

" + "

What's new?

"; break; default: return; } const messageElement = document.createElement('div'); messageElement.classList.add('bot', 'bot-prompts'); messageElement.innerHTML = message; botCon.appendChild(messageElement);}function getPathCustomization(path) { const validLocales = ['en', 'en-us', 'en-ie', 'en-gb', 'en-ca']; // Example usage if (!isValidHostAndLocale(validLocales)) { // Dont attempt to fire any path customization if the host or locale is invalid. return; } if (path.length <= 6) { const lastState = localStorage.getItem('buzzLastState'); if (lastState) { return; } botTransitionMid(); scrollToBottom(); // Handle the case when the path is less than 6 characters } else if (path.includes('search/fluke')) { const lastState = localStorage.getItem('buzzLastState'); if (!lastState) { botTransitionMid(); } // Get the content of input.alg-search-input. We'll use this instead of query params because they are more accurate. let searchInput = document.querySelector('input.alg-search-input'); let botInput = document.getElementById('user-input'); // Function to build and insert CTA function buildAndInsertCta(searchValue) { let algoliaContainer = document.querySelector('.alg-full-results'); let builtCta = "

Try the Fluke assistant to learn more about \"" + searchValue + "\"

"; algoliaContainer.insertAdjacentHTML('afterbegin', builtCta); botInput.value = "Please tell me more about " + searchValue; } // If the search input has a value, we want to update the CTA and the bot input field if (searchInput) { // Now find the algolia container we will be adding the CTA to let algoliaContainer = document.querySelector('.alg-full-results'); // If the container exists, we place the CTA and update the value if (algoliaContainer) { // Check to see if .buzz-algolia exists. If it does, we want to update the CTA and the bot input field let existingCta = document.querySelector('.buzz-algolia'); if (!existingCta) { buildAndInsertCta(searchInput.value); } } // Additionally, when the input changes we change the CTA and the bot input field to keep them in sync searchInput.addEventListener('input', function () { let currentCta = document.getElementsByClassName('toc-cta')[0]; if (currentCta) { currentCta.innerHTML = "Try the Fluke assistant to learn more about \"" + searchInput.value + "\""; botInput.value = "Please tell me more about " + searchInput.value; } else { buildAndInsertCta(searchInput.value); } }); // If .buzz-algolia exists, we are gonna add a click event listener to the button let algoliaCta = document.querySelector('.toc-cta'); if (algoliaCta) { algoliaCta.addEventListener('click', function () { // If the bot-container isnt bot-mid or bot-full, we want to transition to bot-mid if (!document.querySelector('.bot-container').classList.contains('bot-mid')) { botTransitionMid(); } sendMessage(botInput.value); // Clear the input field botInput.value = ''; }); } } // Handle the case when the path contains 'search/fluke' } else if (path.includes('products/electrical-testing/digital-multimeters')) { const lastState = localStorage.getItem('buzzLastState'); if (lastState) { return; } botTransitionMid(); scrollToBottom(); // Handle the case when the path contains 'products/electrical-testing/digital-multimeters' }}function getOrGenerateChatId() { let chatId; chatId = localStorage.getItem('chatId'); // If chatId does not exist in localStorage, generate a new one if (!chatId || chatId === '') { chatId = 'chat-' + Date.now() + '-' + Math.floor(Math.random() * 1000); localStorage.setItem('chatId', chatId); } return chatId;}// Clear chat functionfunction clearMessages(path) { localStorage.removeItem('chatMessages'); localStorage.removeItem('chatId'); localStorage.setItem('chatQuestion', 0); // Reset to 0 localStorage.removeItem('buzzLastState'); chatId = getOrGenerateChatId(); sendDataLayer({ 'event': 'chat_bot_event', 'chatId': localStorage.getItem('chatId'), 'reponseCount': localStorage.getItem('chatQuestion'), 'requestType': 'clear_chat' }); const botCon = document.querySelector('.bot-message-container'); // After clearing the chat we want to remove the innerHTML of the bot-message-container, and add the intro text again botCon.innerHTML = ""; addInitialBuzz(path);}function appendSentiment(thumbs, chatId, chatDialogId) { const botCon = document.querySelector('.bot-message-container'); const lastBotMessage = botCon.querySelector('.bot:last-of-type'); if (thumbs) { const botRatingDiv = document.createElement('div'); botRatingDiv.classList.add('bot-rating'); // Insert bot rating div after lastBotMessage lastBotMessage.parentNode.insertBefore(botRatingDiv, lastBotMessage.nextSibling); // Insert buttons inside bot rating div botRatingDiv.innerHTML = ` `; const thumbupElements = botRatingDiv.querySelectorAll('.thumbup'); const thumbdownElements = botRatingDiv.querySelectorAll('.thumbdown'); thumbupElements.forEach((thumbup) => { thumbup.addEventListener('click', function () { chatRating = 1; this.classList.add('responded'); thumbdownElements.forEach((thumbdown) => thumbdown.classList.add('responded-alt')); thumbupElements.forEach((thumbup) => thumbup.style.pointerEvents = 'none'); thumbdownElements.forEach((thumbdown) => thumbdown.style.pointerEvents = 'none'); // Call your sendRating function with appropriate parameters sendRating(chatRating, chatId, chatDialogId) }); }); thumbdownElements.forEach((thumbdown) => { thumbdown.addEventListener('click', function () { chatRating = -1; this.classList.add('responded'); thumbupElements.forEach((thumbup) => thumbup.classList.add('responded-alt')); thumbupElements.forEach((thumbup) => thumbup.style.pointerEvents = 'none'); thumbdownElements.forEach((thumbdown) => thumbdown.style.pointerEvents = 'none'); // Call your sendRating function with appropriate parameters sendRating(chatRating, chatId, chatDialogId) }); }); }}// Function to send user message to Azure Chatbotfunction sendRating(chatRating, chatId, chatDialogId) { const endpoint = 'https://flk-delphiapi-sitegpt-prd-001.azurewebsites.net/v1/chat/ratings'; const payload = { chatId: chatId, dialogId: chatDialogId, chatRating: chatRating, }; const headers = { 'Content-Type': 'application/json', 'Ocp-Apim-Subscription-Key': '078db2f23dcb4b23a5cb1b6255fc08c8', }; // Add this line at the beginning of your function to record the start time const startTime = new Date(); fetch(endpoint, { method: 'POST', headers: headers, body: JSON.stringify(payload), }) .then(response => { if (!response.ok) { throw new Error(`HTTP error! status: ${response.status}`); } return response.json(); }) .then(data => { if (data) { console.log('sent rating ' + chatRating + ' for question ' + chatDialogId); } }) .catch(error => console.error('Error:', error));}function cloudflareTestingPortal(botResponse, timeTakenInSeconds, payload, dataLayerObject) { //Get the hostname const hostname = window.location.hostname; // If the hostname is uat-gpt.fluke.com, add a console message if (hostname === 'uat-gpt.fluke.com') { // Add the botResponse, timeTakenInSeconds, payload, and gtm the respective containers // last-message-right, last-response-right, data-layer-right, payload-right const lastMessageRight = document.querySelector('#last-message-right'); const lastResponseRight = document.querySelector('#last-response-right'); const dataLayerRight = document.querySelector('#data-layer-right'); const payloadRight = document.querySelector('#payload-right'); lastMessageRight.innerHTML = botResponse; lastResponseRight.innerHTML = timeTakenInSeconds; dataLayerRight.innerHTML = JSON.stringify(dataLayerObject); payloadRight.innerHTML = JSON.stringify(payload); }}// We need to pass datalayer stuffiesfunction sendDataLayer(data) { // Function for event tracking window.dataLayer = window.dataLayer || []; window.dataLayer.push(data);}// For global launch, we are only supporting en-us for many of the Kaizen specific features. function isValidHostAndLocale(validLocales) { // Get the hostname - currently only supported on *.fluke.com. The first path segment is the lang-locale, and we are only supporting en-us at launch const hostname = window.location.hostname; const path = window.location.pathname; const langLocale = path.split('/')[1]; // If the hostname is not 'www.fluke.com' or 'regression.fluke.com', or the langLocale is not in the validLocales array, return false if ((hostname !== 'www.fluke.com' && hostname !== 'regression.fluke.com') || !validLocales.includes(langLocale)) { return false; } // If the hostname and langLocale pass the conditions, return true return true;}