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Resistance: Resistance of a conductor is the opposition offered by the conductor to the flow of current through it. Resistances are of two type fixed resistance and variable resistance. Reason of resistance: The resistance is due to collision of moving electrons while moving from negative terminal to positive terminal. In this process when electrons collide with positive ions , few electrons drift away and do not reach to the positive terminal. Because of this drifted electrons the conductance of the conductor decreases and therefore resistance results in this process. Conductance = 1 / resistanceRt=R0 ( 1+ α t) ohm.
where t = Tt - T 0
Where Rt = Resistance at temperature t 0C
R0 = Resistance at temperature 00C
α = temperature Co-efficient of resistance of a particular conductor.
Temperature Co-efficients (α)Conductor MaterialTemp. Co-efficentUnitCopper4.041 x 10-3Ohm-mAluminium4.308 x 10-3Ohm-mResistance formula from the relation of potential difference and current is given below.
R…

Potential Difference: Potential difference between two terminal of a conductor is the work done while carrying unit positive charge from one terminal to the other terminal.

Unit of the potential difference is volt.
V = W / Q
or 1 V = 1JC-1
1 Volt is equal to 1 Jouls/coulomb.
and W = QV
Above equations should be memorized
Potential difference is measured by voltmeter. If the VA and VB be the potential of the two end of a conductor then we can write
VA - VB = W /Q

प्राकृतिक आपदा पर निबंध प्रकृति द्वारा जो आपदा आती है वह बहुत ही भाया वह होती है । इसका आकार बहुत बड़ा होता है। अनेक आपदाओं में से बाढ़ और भूकंप बहुत बार होता रहता है। हाल ही में चेन्नई में बाढ़ आया जो दक्षिण भारत को अस्तव्यस्त करके रख दिया । इसका प्रभाव मानव जीवन पर इस तरह हुआ कि मानो जीवन रुक गया है। घरों का पहला तल्ला पूरा पानी में डूब गया । ट्रेन बस वायुसेवा टेलीफोन ए टी एम बैकिंग आदि एकदम बन्द हो गया था । सबसे भयानक है टेलीफोन सेवा का बन्द होना। क्योंकि सूचनाए मिलना बन्य हो जाती है। किसी तरह सरकार की सहायता से बहुत लोगों की जान बचाई जा सकी । फिर भी अधिक लोगों की मृत्यु हो गई । इन सभी प्राकृतिक आपदाओं से हमें सीखना होगा कि किस प्रकार प्रकृति पर बिना कारण के बोझना डालें। नहीं तो प्रकृति का असंतुलन मनुष्य पर बहुत भारी पड़ेगा । हमें प्रकृति का संतुलन बनाए रखने के उपाय सोचने चाहिए । ऐसे कार्यो को नहीं करना चाहिए जिससे प्रकृति गुस्से में आए और बड़ा सर्वनाश कर जाए ।

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Ratio Mathematics ICSE Tutorial Class 7

There are four videos of Ratio class 7. Few sums have also been explained with very easy steps. If there are any doubts then comment below. We will try to clear those doubts.

1. Understanding Ratio:


2. Comparing Ratio Basic and Shortcut method:

3. Compound Ratio , continued Ratio Dividing a number in a given Ratio:

4. Solution of few problem of ratio:
These sums of Ratio class 7 have been discussed in this video:
1. write in simplest form
72:108, 1/6:1/2,
15cm to 4m.
2. Population of a village is 32400. The ratio of literate
to illiterate person in the village is 11:7. Find the actual number of literate person and illiterate person. .
3. If a, b and c are three numbers such that a:b=4:9 and b:c=27:35. Find a:c
4. In what ratio should we increase 650 to obtain 1000.