Unknown Resistance
Unknown Resistance - Related Videos
15:03
Identification of Unknown Aldehydes and Ketones - Student Protocol
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2020
Source: Lara Al Hariri and Ahmed Basabrain at the University of Massachusetts Amherst, MA, USA DNPH Test for Aromatic Aldehydes and KetonesExpand In this lab, you'll use the DNPH test, the Tollens' test, and the iodoform test to identify two unknown aldehydes or ketones. You'll use butanone and benzaldehyde as known compounds to confirm that the tests are working as expected. You'll start the lab with the DNPH test, which relies on the reaction between 2,4-dinitrophenylhydrazine, or DNPH,...
06:48
Identification of Unknown Aldehydes and Ketones - Instructor Prep
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2020
Source: Lara Al Hariri at the University of Massachusetts Amherst, MA, USA Preparation of Test SolutionsExpand Here, we show the laboratory preparation for 10 students working in pairs, with some excess. Please adjust quantities as needed. Before you start, put on a lab coat, splash-proof safety glasses, and nitrile gloves. Note: DNPH is a shock explosive, so handle it gently with low friction tools. Phosphoric acid is also toxic and corrosive. Prepare 100 mL of a 0.1 M...
03:09
Identification of Unknown Aldehydes and Ketones - Concepts
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2020
Aldehydes and Ketones Aldehydes and ketones have a carbonyl group (C=O) as a functional group. A ketone has two alkyl or aryl groups attached to the carbonyl carbon (RCOR’). The simplest ketone is acetone, which has two methyl groups attached to the carbonyl carbon (CH3COCH3). An aldehyde is similar to a ketone, except that instead of two side groups connected to the carbonyl carbon, they have at least one hydrogen (RCOH). The simplest aldehyde is formaldehyde (HCOH), as it has two hydrogens...
08:53
Freezing-Point Depression to Determine an Unknown Compound
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2023
Source: Laboratory of Lynne O' Connell — Boston College When a solid compound is dissolved in a solvent, the freezing point of the resulting solution is lower than that of the pure solvent. This phenomenon is known as freezing-point depression, and the change in temperature is directly related to the molecular weight of the solute. This experiment is designed to find the identity of an unknown compound by using the phenomenon of freezing-point depression to determine its molecular weight. The...
01:21
Testing a Claim about Mean: Unknown Population SD
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2023
A complete procedure of testing a hypothesis about a population mean when the population standard deviation is unknown is explained here. Estimating a population mean requires the samples to be approximately normally distributed. The data should be collected from the randomly selected samples having no sampling bias. There is no specific requirement for sample size. But if the sample size is less than 30, and we don't know the population standard deviation, a different approach is used; instead...
FAQs
Under the stated Ohm’s law approach, resistance is obtained by dividing the applied voltage by the current that results, R = V/I. For a given applied voltage, a larger calculated value indicates greater opposition to current because the measured current is smaller. This ratio converts electrical measurements into a component-specific resistance value for circuit analysis.
A Wheatstone bridge identifies the unknown by comparing it with known resistances rather than relying only on a single voltage and current reading. The bridge reaches balance when the ratios of the known resistances match. That balance condition provides the basis for calculating the unknown value and can improve measurement accuracy in experimental physics.
These variables influence electrical conduction, so they can change the resistance associated with a wire, sensor, or other component. Connection conditions also matter when interpreting the result. Consequently, an experiment should treat temperature, material, geometry, and connections as relevant conditions to assess or record when comparing resistance measurements or explaining differences between components.
Use a known voltage and measure the current produced by the component, then evaluate R = V/I. The calculated ratio is meaningful in relation to the voltage and current used, so those measurements should correspond to the same circuit condition. This workflow supports direct characterization before comparing the result with expected circuit behavior.
A direct calculation is appropriate when the applied voltage and resulting current can be measured for the component. A Wheatstone bridge is useful when greater accuracy is desired, because the unknown is determined from a balance condition involving resistance ratios. Choosing between them therefore depends on whether straightforward measurement or a more accurate comparison is the experimental priority.
It provides a way to characterize wires, sensors, and electronic components, while also testing whether a circuit behaves as expected. Measurements can be compared across different temperatures, materials, geometries, or connection conditions to examine their effects on conduction. The resulting resistance values connect quantitative circuit analysis with experimental study of component and material behavior.