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# current which passes through the battery    # 6

Posted on 2006-11-08
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6.      The emf and the internal resistance of a battery are as shown. When the terminal voltage of the battery is 20V , the current which passes through the battery including direction is closest to :
Solution :  6 A , from a to b.

is it correct ?
0
Question by:c_hockland
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LVL 84

Expert Comment

ID: 17904562
You probaly need to use Ohm's law and Kirchoff's Laws
0

LVL 18

Expert Comment

ID: 17906048
V = IR
so
I = V/R

V=20V
Internal resistance R = 20/6 v/A?
0

Author Comment

ID: 17906207
JR2003 , are u asking me ? or this is the answer ?
"...R = 20/6 v/A?    "
0

LVL 18

Expert Comment

ID: 17906280
You haven't described the circuit.
Is there anything else in the circuit apart from a wire with no resistance and a battery with internal resistance?
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Author Comment

ID: 17906288

|_______________________________________
|                                                                    |
A_________| |______/\/\/\/\/\/\/\/___________B
|                                                                    |
|                                                                    |
|                                                                    |
________________________________________

0

LVL 18

Expert Comment

ID: 17906346
What does it say the internal resistance of the battery is?
0

Author Comment

ID: 17906370
sorry my fault..

R=2 Ohm
battery is 12V
0

Author Comment

ID: 17906379
|_______________________________________
|                                                                    |
A_________| |______/\/\/\/\/\/\/\/___________B
|                  12V               2Ohm                     |
|                                                                    |
|                                                                    |
________________________________________
0

LVL 18

Expert Comment

ID: 17906445
V=IR
so
I=V/R
= 12/2
=6 Amps
0

LVL 84

Expert Comment

ID: 17906448
based on that diagram
V = IR
12V = 6A 2Ohm
but where does the 20V come in
0

Author Comment

ID: 17906939
any ideas ?
0

LVL 84

Expert Comment

ID: 17907066
In one place you said 12V, in another place you say 20V
Was one of them wrong, or were they measured at different places?
0

Author Comment

ID: 17907097
6.      The emf and the internal resistance of a battery are as shown. When the terminal voltage of the battery is 20V , the current which passes through the battery including direction is closest to :    (solution manual)  6 A , from a to b.
and then he gave us the sketch

0

LVL 39

Expert Comment

ID: 17907641
which side of the battery terminal is positive/negative?
How is the 20V applied to the battery (eg: positive to positive, or positive to negative)?
0

Author Comment

ID: 17907649
|_______________________________________
|                                                                    |
A_________| |______/\/\/\/\/\/\/\/___________B
|                  12V               2Ohm                     |
|               +    -                                              |
|                                                                    |

0

LVL 39

Accepted Solution

ID: 17908267
|----------------------------------------------------|
|                                                                 |
|                                                                 |
A------------||-------C------/\/\/\/\/\/\/\---------B
|           +  12V  -                  2 Ohm              |
|                                                                 |
|<<<<<<<<<<<  +  20V  -  >>>>>>>>>> |

If 20V is applied to the battery as shown, then
point C has 8 V over point B
V=IR
8 V = I * 2 Ohm    =>   I = 4A (from A to B)
(the current through the ideal battery part and the battery resistance part are equal)
0

LVL 16

Expert Comment

ID: 17910381
Some good information on the subject:

http://www.buchmann.ca/Chap9-page1.asp
0

Author Comment

ID: 17924995
any ideas ?  i have two solutions here , one with 6 A and one with 4 A..which one is the correct ?

note: the emf of the battery is 12 V but the we want to find the the current when the terminal voltage of the battery is 20V

any ideas?
0

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