Diodes question Watch

chaosdestro0
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#1
Report Thread starter 7 years ago
#1
Because there is not a electronics section, this seemed the closest place to ask this question.

I am getting a bit confused on diodes and I am not sure if this is the correct answer. ( the mark scheme does not give a diagram)
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Stonebridge
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#2
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That circuit will work fine as a full wave rectifier with smoothing. (Smoothing capacitor C)
It's called a "bridge" rectifier circuit.
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chaosdestro0
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#3
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(Original post by Stonebridge)
That circuit will work fine as a full wave rectifier with smoothing. (Smoothing capacitor C)
It's called a "bridge" rectifier circuit.
The next question is a bit weird, I am not sure if that means T1 and T2 or just T1.


If it means T1+T2 would you use this?
T = 0.69 (R1+2R2) x C
3=0.69(90000)C
3=62100C
C=3/62100
C=48.3 *10^-6
However the answer given is this, I don't understand why they have written the 47.6 *10^-6 part.
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Stonebridge
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#4
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According to this
http://en.wikipedia.org/wiki/555_timer_IC#Astable_mode
you have the correct formula and answer. It's 48uF to 2 significant figures.
I'm not sure what your problem is here.
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chaosdestro0
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#5
Report Thread starter 7 years ago
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(Original post by Stonebridge)
According to this
http://en.wikipedia.org/wiki/555_timer_IC#Astable_mode
you have the correct formula and answer. It's 48uF to 2 significant figures.
I'm not sure what your problem is here.
The problem is that it seems as if the mark scheme has 47.6u to three significant figures, where as I get 48.3u to three significant figures.
Perhaps I am being pedantic, but I must have gone wrong somewhere or they have.
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Stonebridge
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#6
Report 7 years ago
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It depends what value to take for Ln 2
0.69 is only to 2 sig figs. (Which you used)
0.693 to 3 figures
My calculator gives 0.6931471
You should use the the most accurate value in the calculation and round up or down at the end.
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chaosdestro0
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#7
Report Thread starter 7 years ago
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(Original post by Stonebridge)
It depends what value to take for Ln 2
0.69 is only to 2 sig figs. (Which you used)
0.693 to 3 figures
My calculator gives 0.6931471
You should use the the most accurate value in the calculation and round up or down at the end.
I see, I never knew that 0.69 was not the most accurate value to use, but I guess they tweak the questions so that it is not a problem.
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