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Write differences between resistance and resistivity?

Posted by Priyanshu Singh 6 years, 3 months ago

1 answers

Yogita Ingle 6 years, 3 months ago

Sl. No.	Differentiating Property	Resistance	Resistivity
1	Definition	Resistance is the physical property of a substance because of which it opposes the flow of current i.e. electrons.	Resistivity is the physical property of a particular substance which is having particular dimensions.
2	Proportionality	Resistance is directly proportional to the length and temperature while it is inversely proportional to the cross-sectional area of the material.	Resistivity is only proportional to the nature and temperature of the particular material.
3	Symbol	R	ρ
4	Formula	R = V/I or, R = ρ(L/A) V = Voltage, I = Current, ρ = Resistivity	ρ = (R×A)/L R = Resistance, L= Length, A = Cross-sectional area
5	SI Units	The SI unit of resistance is Ohms	The SI unit of resistivity is Ohms-meter.
6	Applications	The property of resistance is used in several places like heaters, fuses, sensors, etc.	Electrical resistivity measurement is used as a quality control test for calcareous soil.

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ANSWER

Explain joules law of heating?

Posted by Priyanshu Singh 6 years, 3 months ago

CBSE > Class 10 > Science

2 answers

Yogita Ingle 6 years, 3 months ago

Joule’s law of heating states that when a current ‘i ' passes through a conductor of resistance ‘r’ for time ‘t’ then the heat developed in the conductor is equal to the product of the square of the current, the resistance and time.

H = i² rt

The reason behind the heat produced is the collision of the free electrons with the lattice ions or atoms while accelerating in presence of the external electric field.

we know that

volt= work done/ total charge or v = w/q

from this we get w= vq

we know that current i = q / t

so q = it

putting this in prev equation

we get w = vit

from ohms law v = ir

putting it in prev eq we get

w = irit = i²rt joule as work is stored as heat soH = I²RT Joules

1Thank You

Veenu Kodan 6 years, 3 months ago

According to joules law of heating the heat produced in a wire is directly proportional to: 1.)square of current(I) 2.)resistance of wire(R) 3.)time,for which the current is passed(t) H=I^2×R×t

2Thank You

ANSWER

The star twinkling but planet no twinkling why?

Posted by Aditya Puri 6 years, 3 months ago

CBSE > Class 10 > Science

4 answers

Yash Chaudhary 6 years, 3 months ago

Because star is so far and changing the atmosphere median is also change by changing the median the light is refracted and star is twinkling but planet is not so far than star

1Thank You

Sahil ??? 6 years, 3 months ago

Planet is a collection of point sources of light.Different point sources of planets twinkle at different time period.The dim light effect caused by some point sources are nullified by the bright light of otge point sources....

1Thank You

Aditya Goarsia 6 years, 3 months ago

Stars are far from from india and planets are near india

1Thank You

Veenu Kodan 6 years, 3 months ago

The continuously changing atmosphere is unable to cause variation in the light coming from a big size planet due to refraction because of what's the planets do not Twinkle at all.

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