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An energy saver light bulb of 11 W gives the same illumination as a conventional 60W light bulb. (a) If a typical light bulb is used on average for five hours a day, how much energy is saved per year by one light-bulb? (b) If each household used eight such light-bulbs, ad there are 20 million households in a country, how much energy would that country save annually?
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What is the effective resistance between P and Q in the diagram?
Asked Malik Ahmed
Answer : 8 ohms
The Two arms have resistances 32 ohm and are in parallel, Their effective resistance is 1 ohms. This is in parallel with the middle arm. So the effective resistance is 8 ohms.
The three arms have resistances 32, 1 and 32 respectively and are in parallel. Therefore, taking their reciprocals and adding will give the answer.
We know that at 0K all the electrons will be in valence shell of semiconductors………..is it the case with even metals?
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Two different wires X and Y of same diameter but different materials are joined together in series across a battery . If the number density of electrons in X is twice that in Y . Find ratio of drift velocity of electrons in two wires .
In series combination, the current is the same.
I = nAev
=> n1v1 = n2 v2
=> v1:v2 =n2:n1