By what method will a positively charged rod produce a negative charge on a conducting sphere that is placed on an insulating surface?
For some reason, everywhere I search they say the correct answer is "c". However, I can't see how the sphere can be charged by induction since it is placed on an insulating surface.
If I were you I would answer d.
23) A 4.0 μF and a 6.0 μF capacitor are connected in series across an 8.0-V DC source. What is the charge on the 6.0 μF capacitor?
A) 2.0 μC B) 4.0 μC C) 25 μC D) 19 μC
The capacitors are connected like this: ---ll--ll---
There are two rules that we must take into acount:
1)The charge Q of each capacitor is the same (Q1=Q2) (it is explained in the link provided below)
2) the two capacitors can be
equalized with a
single capacitor in which: the capacity is 1/C = 1/C
1 + 1/C
2If you find
the charge of this equalizing capacitor, it will be
equal with the charge of capacitor 1 and equal with the charge of capacitor 2 (
Q=Q1=Q2)
So we firstly find the capacity C (of the equalizing capacitor): 1/C = 1/C
1 + 1/C
2 <=>1/C=1/4 + 1/6 <=> 1/C = 3/12 + 2/12 <=> 1/C = 5/12 <=> C=12/5=2,4μF=2,4*10
-6F.
Now, we find Q: C=Q/V <=> Q=C*V=2,4*10
-6*8=19,2*10
-6C or around 19μC. So, Q1=Q2=19μC
If you don't understand something, check this:
http://farside.ph.utexas.edu/teaching/302l/lectures/node46.html (specifically the last paragraph, under figure 16) and if you still don't understand you can ask anything.
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