What is resistor made of

Usually the resistive materials are considered proprietary. Thin film resistors are formed by vapor deposition of a thin layer of resistive material onto a base.

Thick and thin film resistors are normally trimmed to a specific value by etching away resistive material using lasers, sandblasting, etc. Most composition and wire-would fixed resistors are packaged in a cylindrical form with axial leads. Thick and thin film resistors are manufactured in a variety of shapes and sizes.

Film resistor networks are packaged in plastic dual-in-line packages DIP , single-in-line packages SIP , flatpack packages and round metal packages identical to those in which integrated circuits are packaged. Individual resistors may be packaged in chip and pellet form. A chip, as used in microelectronics, is any small usually square or oblong piece of material that contains a circuit or component. Thick film resistors are commonly used in hybrid circuits where they are deposited directly onto the circuit substrate.

A substrate is a tiny platform on which circuitry is deposited. Thick and thin film resistors have found many applications in the development of microelectronics because they can be made smaller than other comparable value resistor types.

Film resistors are often used in critical positions in circuitry. Power Resistors - Power resistors are required to carry large quantities of current and subsequently dissipate a lot of heat.

Consequently they are usually larger than those that are designed to carry smaller current quantities. Power resistors are usually encapsulated in materials that aid in the dissipation of heat and are usually designed so they can be mounted to a heatsink or equipment chassis to facilitate heat removal by conduction. Common power resistors may be composition, wire-wound, or film resistors. Variable Resistors - A variable resistor is commonly referred to as a 'pot'; meaning a potentiometer.

A potentiometer contains an element of continuous resistive material with a sliding contact that traverses the element in a circular or straight line, depending on the potentiometer style. It is normally adjusted by a shaft connected to a dial or thumbscrew, or by a screw-driver or adjustment tool. Variable resistors may be wire-wound, composition or film resistors.

Small, precision, adjustable resistors are called 'trim-pots' and are used for fine adjustments in low current applications. Variable resistors that are constructed to carry large values of current or power are called 'rheostats' and are commonly used for adjusting motor speeds and oven and heater temperatures. Resistors usually have markings indicating value, tolerance and sometimes composition and reliability rating.

Reliability rating is given as a failure-rate in percentage failure per hours of operation. These values may be written on the resistors or may be provided in color code as shown on the carbon composition resistor in Figure 1. Figure The color code is usually provided by four or five color bands represented by the variation in color shades in the black and white photo around the body of the resistor.

An interpretation of this color code is given in Table 1. The color code given is the military standard general code for color bands or dots used on electronic parts and used by most manufacturers. Figure 2 Figure depicts some resistor types commonly used in medical device circuitry. As you can see, the metal film, wire- wound and composition resistors on the left look essentially alike.

This makes it extremely difficult to identify resistor construction by simple observation, unless the observer is familiar with the manufacturer's product.

The variation in size within each resistor group shown is due to variation in power rating and value. Usually, within a resistor type, the higher the power rating watts the larger the resistor.

But a particular wattage in one resistor type may be larger or smaller than the same wattage in another type.

For example, the largest carbon composition resistor shown is 2 watts, while the wattage of the wire- wound resistor directly above it is 3 watts, although the carbon resistor is slightly larger than the wire-wound resistor.

Determine value by starting with color closest to end of resistor. If colors equidistant from both ends, begin at end farthest away from gold or silver tolerance band. The proposed Medical Device GMPs would require that electronic components when appropriate, be inspected, sampled, and tested for conformance with specifications. The following resistor tests are those which may be conducted routinely by manufacturers of critical medical devices. Resistance Value - The value of the resistor is measured using an ohmmeter or resistance bridge to verify the resistance value is within the tolerance specified in the resistor specifications.

Resistance to solvents - Some firms conduct a solvent resistance test to verify that the component markings will not be discolored or removed when subjected to production cleaning solvents. The test is also conducted to verify that the solvents will not damage the component material or finish. Solderability - The purpose of the solderability test is to determine if the component leads are receptive to the soldering process.

Basically this test determines if solder will adhere completely to the component leads. Burn-in - This test is sometimes conducted on thick and thin film resistors and resistor networks See ITG A load resistor is a resistor selected for a specific purpose. For example, it you want to put a load on an audio amplifier made to drive an 8 ohm speaker to 50 watts, then your load resistor would be a 8 ohm 50 watt resistor.

If you want a load resistor to terminate a 50 ohm line, you would need a 50 ohm resistor, although in this case, you probably want one that is part of a co-ax connector. A load resistor for an op-amp output is typically 2k, since most op-amps are rated for 10 volts at 5 mA. Etc, etc. The alternator does not have a resistor. It does not have a ballast resistor. RMS value is defined as "The amount of ac supply required to make same heat effect in resistor , which is made by dc current, in that resistor".

The purpose of colored bands on a resistor is to tell whoever is installing the resistor the amount of resistance that particuliar resistor has. A non-ohmic resistor doesn't have a constant resistance.

A ohmic resistor has a constant resistance. A cement resistor is typically used as a power resistor a resistor whose power rating is greater than 1 W. Because copper is a very good conductor, it isn't used for making the main body of a resistor. The body must be made of high resistance metals, such as nickel and chrome alloys. Copper is only used for making the connecting leads of a resistor. Variable resistor is an resistor that can change its resistance manually, by rotating a handle or a screw.

In series with the resistor. It does not have an ignition ballast resistor. A voltmeter can be connected in parallel with a resistor to show the voltage across the resistor. Log in. See Answer. Best Answer. Study guides. Q: What is a resistor made from? Write your answer Related questions. Who made the first resistor? When and by who were resistors made?

What are resistor and variable resistor? Made from a variety of materials such as carbon this inhibits the flow of current? What is a variable resistor made from? Carbon composition is the oldest design and usually the cheapest of the resistors.

Carbon granules are mixed with a filler material and inserted into a tubular casing. In earlier types vulcanised rubber was used but in modern designs the carbon is mixed with a ceramic filler. The value of resistance is determined by the amount of carbon added to the filler mixture. Carbon composition resistors do not have the close tolerances of either carbon or metal film types.

One advantage however is that they are better suited to applications involving large voltage pulses than the more modern types. Carbon composition, carbon and metal film resistors are available in a range of power ratings, from 0. In a resistor, the power that the resistor must dissipate get rid of as heat depends on the voltage difference V across the resistor, and the current I flowing through it.

For any particular type or value of resistor, the greater the power rating, the larger the physical size of the resistor. Wirewound resistors are very variable in construction and physical appearance. They are normally available in quite low values of resistance single ohms to a few Kilohms but can dissipate large amounts of power. In use they may get very hot. For this reason high power wirewound resistors may be housed in a finned metal case that can be bolted to a metal chassis to dissipate the heat generated as effectively as possible.

With all types of wirewound resistor, fire protection is important and flame proof cases or coatings are vital. Lead-out wires are normally welded rather than soldered to the resistor. These resistors are made from small rods of ceramic coated with metal such as a nickel alloy or a metal oxide such as tin oxide.

The value of resistance is controlled firstly by the thickness of the coating layer; the thicker the layer, the lower the value of resistance. Also by a fine spiral groove cut along the rod using a laser or diamond cutter to cut the carbon or metal coating effectively into a long spiral strip, which forms the resistor. Note that although the body colour the colour of the laquer coating on metal film resistors is often grey, this is not a reliable guide.