If this voltmeter is connected across a resistor of 20 ohm, how much current is flowing through the resistor?
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Answer:
Solution
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Correct option is A)
The current distributions among the resistors is shown in figure.
Here, I
1
=
9
4.5
=0.5A
As resistor (9,3) and 6 are in parallel so potential across 9+ (potential across 3= potential across 3)
⇒4.5+3I
1
=6I
2
or 4.5+3(0.5)=6I
2
or I
2
=
6
4.5+1.5
=1A
So, I=I
1
+I
2
=0.5+1=1.5A
Equivalent resistance between C and D is R
cd
=(1/10+1/12+1/15)
−1
=4Ω
Potential across C and D is V
cd
=IR
cd
=1.5×4=6V
Potential across A and D is
V
ad
=V
ab
+V
bc
+V
cd
=6I
2
+2I+6=6(1)+2(1.5)+6=6+3+6=15V
This will be the potential across 20Ω as well as the voltmeter because 20Ω is connected in parallel across total resistance across A and D.
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SIMILAR QUESTIONS
star-struck
When a voltmeter is connected across the terminals of a cell, it measure 9 Volt. If a resistance of 1.5Ω is connected across the terminals of a cell as shown in figure. Then current flowing through this resistance is :-
279042
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Medium
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In the circuit shown in figure, E1 and E2 are two ideal sources of unknown emfs. Some currents are shown. Potential difference appearing across 6Ω resistance is V
A
−V
B
=10V.
75221
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Answer:
15
The current distributions among the resistors is shown in figure.
Here, I
1
=
9
4.5
=0.5A
As resistor (9,3) and 6 are in parallel so potential across 9+ (potential across 3= potential across 3)
⇒4.5+3I
1
=6I
2
or 4.5+3(0.5)=6I
2
or I
2
=
6
4.5+1.5
=1A
So, I=I
1
+I
2
=0.5+1=1.5A
Equivalent resistance between C and D is R
cd
=(1/10+1/12+1/15)
−1
=4Ω
Potential across C and D is V
cd
=IR
cd
=1.5×4=6V
Potential across A and D is
V
ad
=V
ab
+V
bc
+V
cd
=6I
2
+2I+6=6(1)+2(1.5)+6=6+3+6=15V
This will be the potential across 20Ω as well as the voltmeter because 20Ω is connected in parallel across total resistance across A and D.