Resistance, Physics

Assignment Help:

RESISTANCE:

An electric current is a flow of free electrons through a conductor. The size of current flowing through a conductor for a given applied voltage depends on:

• The number of free electrons.
• The opposition to free movement of the electrons caused by the structure of the material.

These two factors taken together give an effective opposition to current flow which is called resistance. To simplify matters it is usual to ignore the second factor and equate good conductors to a large number of free electrons and poor conductors to fewer free electrons. Hence, a good conductor is a material which has low resistance, i.e. a large number of free electrons, and allows a large current to flow. Conversely a poor conductor has a high resistance, i.e. few free electrons and allows only a small current to flow for the same applied voltage. Because the value of the current flowing is determined by the resistance in the circuit, current flow can be controlled by varying the resistance.

Even the best conductors have resistance.

FACTORS AFFECTING RESISTANCE

The four factors that affect the resistance of a wire conductor are:
• Material. Some materials conduct better than others.
• Length ( ). Resistance is directly proportional to length, thus if the length is doubled (other factors remaining constant), resistance is doubled.
• Cross Sectional Area (A). Resistance is inversely proportional to A. Thus if the cross sectional area is doubled, resistance is halved.
• Temperature. Temperature affects the number of free electrons and hence resistance.

UNITS OF RESISTANCE

Resistance is measured in ohms, symbol ω(omega). The resistance of a piece of material is one ohm if a potential difference of one volt applied across it causes a current of one ampere to flow.


Related Discussions:- Resistance

Explain earth’s magnetic field , As per the most established theory it is b...

As per the most established theory it is because of the rotation of the earth where by the several charged ions there in the molten state in the core of the earth rotate and consti

Explain momentum or linear momentum, MOMENTUM OR LINEAR MOMENTUM. It is...

MOMENTUM OR LINEAR MOMENTUM. It is described as "The product of mass and velocity of the body".                                 OR "The quantity of linear motion of a bod

Find also the power rating of the kettle - conductors, An electric kettle h...

An electric kettle has a resistance of30?. What current will ?ow when it is connected to a 240V supply? Find also the power rating of the kettle   A current of 5A ?ows i

What is the luminous flux of a flashlight, What is the luminous flux of a f...

What is the luminous flux of a flashlight that provides an luminance of 145 lx to the surface of water when held 0.50 m above the water?

Electromagnetism, Your friend has gifted an earphone set to you. While musi...

Your friend has gifted an earphone set to you. While music is on you will try to oppose the two ear phone pieces to attract. Task-I: Will they repel? If yes, why so? Task-II: Why S

Horizontal spring , Normal 0 false false false EN-IN ...

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Car rear ends truck- momentum and collisions, Car Rear Ends Truck Colli...

Car Rear Ends Truck Collisions among objects are governed through laws of momentum and energy. While a collision occurs within an isolated system, the total momentum of the sys

Radio communication , Production of sound messages by a microphone in a rad...

Production of sound messages by a microphone in a radio station (studio). 1) Audio frequency generation. 2) Generation of r.f. carrier wave. 3) Modulation in a transmitter, b) 4

Farad, farad; F (after M. Faraday, 1791-1867) The derived SI unit of c...

farad; F (after M. Faraday, 1791-1867) The derived SI unit of capacitance, described as the capacitance into a capacitor that, if charged to 1 C, contain a potential differenc

Electric field and the associated magnetic field, What the angles among the...

What the angles among the direction are of travel of light the electric field and the associated magnetic field? Answer: The magnetic field created by a changing electric

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd