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Jan 17, 2017

7. Sum of Electrical Power Electrical Energy Consumed by a Resistive Load

Three sums of electrical power have been discussed in this video. This is the second part of sum discussion .

Sum 1: A water heater has a rating of 4 KVA , 240 V.
a) What is the electrical energy consumed by it in:
i)KWhr and
ii) in Joul.
if it is used for 180 minutes.
b) Find the cost of electricity if the rate is
Rs. 7.00 per commercial unit.

Sum 2: The water in an electric kettle took 5 minutes to reach its boiling point when it is connected to 220 v supply.
How long would it have taken if the supply voltage had fallen to 200 v.

Sum 3: What is the resistance under normal working conditions of 240V electric lamp rated at 60 W ? If two such lamps are connected in series across a 240 mains supply, explain why each one appears less bright.

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Dec 23, 2016

6.Sum of Electrical Power Physics Class 10

Three sum of electrical power have been discussed. Here. These sum will give a basic idea of finding electrical power and electrical energy consumed by a load or electrical energy supplied by a source like battery.
The sums are:

1. Two resisters of value 6 ohm and 12 ohms are connected in series across a battery of 12 volt. Draw the circuit diagram and calculate.
a) Current flowing through each resistor.
b) The electrical energy consumed by each resistor.



2. These two resistors again connected in parallel and the above data are again calculated.



3. Two bulb L1 and L2 of rating 100 W 200 V and 10 W 200 Volt respectively are connected across a supply of 200 V in series. Find
a) Current flowing through each bulb
b) which bulb will consume more power.

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Dec 3, 2016

5. Law of Refraction Of Light Physics Class 10

plane-concept

There are two laws of refraction of light. these are :
a) Incident say , refracted ray and normal lie on same plane .
The concept of plane is shown in the image. In terms of x,y and z co-ordinate system , the y-z plane is shown in light sky blue colour. We write on our copy which is considered x-y plane. The image is given just for understanding of plane concept. It is not needed while writing the law. Try to image other planes in the image.



b) Ratio of sin of angle of incidence and sine of angle of refraction remains constant for a pair of media. i.e.

Law of Refraction Of Light Physics Class 10

sin i / sin r = constant (n)
this constant is called refractive index of medium 2 with respect to medium 1.
or we can write
n2 / n 1 = sin i / sin r
Where n 1 is the refractive index of first medium here air. And n2 is the refractive index of second medium here glass.
∴ n2 = n1 x ( sin i / sin r )

If you have any query regarding the laws of refraction then comment below.

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Nov 24, 2016

4. Effects of Refraction of Light Physics Class 10

Effects of Refraction of Light Physics Class 10

There are many effects of the refraction of life in our day to day life. For example I am citing few of them.
a) The partly immersed stick appear to be bend at the surface of the water.
b) The coin kept in water appears raised upward.
c)The water of a pool appear less depth.
d)Stars appear to twinkle in the sky when the sky remains clear.
e)A lemon immersed in water appears to be bigger in size.
All these are discussed in the above video. If you have any confusion then comment below.

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Nov 6, 2016

3 Three Cases of Refraction of Light Physics Class 10

three cases of refraction of light

Case1: When ray of light travels from rarer medium like air to a denser medium like glass then it bends towards normal.

Case 2: When ray of light travels from denser medium like glass to a rarer medium like air then it bends away from the normal.

Case 3: When ray of light travels from rarer medium like air to a denser medium like glass and again emerges to the previous rarer medium then it suffers a lateral displacement as shown in the figure.

emergent ray
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Oct 28, 2016

Keeping Pressure On children for Achieving high Ambition is Right or Wrong उच्चे लक्ष्य को पाने के लिए माता पिता द्वारा बच्चों पर डाला जाने वाला दबाव उचित है या अनुचित है।

लक्ष्य की उंचाई सफलता को गति और उर्जा प्रदान करती है। परन्तु ऐसा लक्ष्य जो किसी बच्चे की क्षमता से अत्यधिक है । वह बच्चे को मानसिक रोगी या पागल बनाता है । और कभी कभी बच्चे आत्महत्या का शिकार हो जाते हैं। इसलिए मेरा मानना है कि इस तरह का दबाव अनुचित है। जब जीवन ही नहीं रहेगा तो जीवन में लक्ष्य का कोई मतलब नहीं है।

जब लक्ष्य बच्चे की क्षमता की परिधि के बाहर होता है , तो वह लक्ष्य उसके लिए बोझ बन जाता है । चुंकि बच्चे अपने माता पिता को खुश देखना चाहते हैं, इसलिए वे झूठ बोलने लगते हैं। जैसे मैने याद कर लिया, होमवर्क कर लिया , मै नकल नहीं करता हूं , मै 90% से जादा अंक प्राप्त करूंगा इत्यादि। इस दबाव में वे अपने अन्दर छुपी मेधा को पररव नहीं पाते । और माता पिता के सोंच के ढांचे में फंस जाते हैं। और नौकरी की खोज में दर दर भटकते रहते हैं। आज के इस प्रतिस्पर्धा के कारण दूसरेआम बच्चे थोड़ा तकनीकी सीखकर रोजी रोटी की दौड़ में इस बच्चे से आगे निकल जाते हैं। और सबसे बड़ी बात यह है कि वे निम्न और कमजोर मानसिकता के शिकार नहीं बनते। मेरे अनुसार ऊंचे लक्ष्य को अपने बच्चे की क्षमता के अनुसार निश्चित करना चाहिए और दबाव न डालकर बच्चों की सहायता करनी चाहिए। उनसे कनेक्ट होना चाहिए। यही मन्त्र उनके जीवन को सफल बना सकता है।

Keeping Pressure On children for Achieving high Ambition is Right or Wrong

माता पिता को मानसिक दबाव न देकर बच्चे से उसके समस्याओं के बारे में बात करने का प्रयास करना चाहिए । ताकि वह समझ सके कि आखिर उनका बच्चा क्यों नहीं अच्छे अंक प्राप्त नहीं कर पा है। ऐसा करने से बच्चे की कमजोरी का पता चल जाता है। जिसपर प्रयास कर के ठीक किया जा सकता है। पढ़ाई की क्रिया के समीप ऐसी बहुत सी बातें होती है, जो बच्चों को सिखाना पड़ता है। जैसे अनुशासन, खुश रहना , स्वस्थ रहने की कला, सामाजिकता पढ़ना -सुनना -लिखने के वृत्त की महत्ता इत्यादि | परीक्षा देने के तरीके सिखाना भी जरूरी है। कुल मिलाकर कहने का तात्पर्य यह है, कि बच्चे के स्थान पर अपने आप को रखकर हमें उसकी परेशानियों को समझना चाहिए। और उसे दूर करने का प्रयास करना चाहिए। अपने बच्चों को अनुशासन उत्साहित करना बहुत महत्वपूर्ण है। इससे वे अपने माता-पिता को सबसे अच्छा मित्र समझने लगते हैं। और अपनी जिम्मेदारी निभाने में अधिक सक्षम बन जाते हैं।

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Oct 19, 2016

2. Causes Of Refraction of Light Physics Class 10

Cause of Refraction : The speed of the light in different transparent substances is different. For example speed of light in air is 3×10⁸ m/s and that of in glass is 2×10⁸ m/s. It is clear that the two speeds of the light are different. When light enters from air to glass the speed of the light gets decreased at the junction of the two media. This change in speed of the light affects the speed the of the various segments of the beam of the light. This can be concluded by the image. This change in speed of the light causes refraction.

Causes Of Refraction of Light Physics Class 10
Therefore the refraction of light is due to the change in the speed of light on going from one medium to another.

Now it is good question why change in speed causes refraction. Here is the answer. If we look the image carefully. The left part of the beam of light enters first into another medium while its right part remains still in first medium here air. Therefore the speed of the left part of the beam experiences speed reduction before that of the right part of the beam. This causes less distance covered by left side beam and more distance traveled by right side beam.

Dear friend if you have any doubt , then comment please. Or you can give your suggestion about this part of the refraction of light.

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Oct 15, 2016

1 Refraction of Light Definition and Introduction Physics Class 10

Refract means bending. The bending of ray of light when it pass from one medium to another medium is known by a term called refraction.

Refraction of Light Definition and Introduction Physics Class 10

Refraction of Light happens due to different speed of light in different medium. Speed of light in air is 3x10⁸m/s and that of in glass is 2x10⁸m/s.

Refraction of Light: It can be defined as the change in the direction of light when it passes from one medium to another medium obliquely.


A transparent substance in which light can travel is called a medium. For example Air, water, glass, kerosene etc are the transparent substances in which light can travel.

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Oct 7, 2016

5.Heating Effect of Electric Current Physics Class 10

heating effect of electric current physics

Current flowing through a conductor produces heat. This heat depends on quantity of current flowing through the conductor, time and resistance of the conductor. We can write:
H α I²
H α R
H α t
By combining these three relation we get:
H α I²Rt
K= (H/(I²Rt))
K= H
for I=1 Amp., R= 1 ohm and t= 1 sec.
K becomes equal to heat generated at this condition. It is found heat generated is 0.24 calorie.
∴ H=0.24 I²Rt

This is also known as Jouls Law of Heating.

Also remember. 1 Calorie = 4.2 Joul

The above video contains explanation of heating effect of current through a conductor. The equation derivation is also shown.

Why 0.24 added while breaking proportionality is clearly explained.

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Important Mathematical Relations of Measurement

mathematical-relationship
Important mathematical relations of measurement.

These are very important mathematical relations. It must be on the tongue of a student . These common relations are seen very frequently in the sum .

| Mass
1 Ton = 10 Quintals 1 Quintal = 100 Kg
1 Kg = 1000 g 1 pound = 453 g
Distance
1 Km = 1000 m 1m = 100 cm
1 feet = 12 inches 1 inch = 2.54 cm
1 yard = 3 feet
Time
1 year = 365 days 1 month = 30 days
1 week = 7 days 1 hour = 60 min
1 min = 60 seconds 1 day = 24 hours
Countable
1 gross = 144 1 dozan = 12
Re 1 = 100 Paise
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