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Question in attachment!!!
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Answers
In the above Question ,
[ 1 ] . Resistance between R and S
Here , let us observe the figure carefully.
The resistors RY and YS are in series .
When, resistances are in series , the equivalent resistance is the sum of the resistances.
So ,
=> 1.5 Ohm + 1.5 Ohm
=> 3 OHm .
Now , this is parallel with RS = 1.5 Ohm
For parallel resistances -
Equivalent Resistance = R1 × R 2 / { R 1 + R 2 }
=> { 3 × 1.5 } / 4.5
=> 4.5 / 4.5
=> 1 Ohm ....... A 1
Now,
Resistances in series with XY
=> 1.5 Ohm + 1.5 Ohm + 1 Ohm + 1.5 Ohm + 1.5 Ohm
=> 7 Ohm
This is parallel to ( 1.5 Ohm + 1.5 Ohm = ) the 3 Ohm resistance .
Hence ,
Net resistance between X and Y
=> 7 × 3 / { 7 + 3 }
=> 2.1 Ohm ... A 4
Now , resistances In series CD
=> 2.1 Ohm + 1.5 Ohm + 1.5 Ohm
=> 5.1 Ohm
This is parallel to the ( 1.5 Ohm × 3 = ) 4.5 Ohm resistance .
Equivalent resistance between C and D
=> ( 5.1 × 4.5 ) / ( 9.6 )
=> 2.390625 Ohm ...... A 3
Now , resistances in series , PQ
=> 1.5 Ohm + 1.5 Ohm + 2.390625 Ohm
=> 5.390625 Ohm ...... A2
___________
Answer -
I ) 1 Ohm
2 ) 5.390625 Ohm
3 ) 2.390625 Ohm
4 ) 2.1 Ohm
Concept Used:
- Equivalent resistance in series combination is given by
- R = R1 + R2 ... --------( 1 )
- Equivalent resistance in parallel combination in given by
- R = (R1.R2 )/( R1 + R2 ) ---------( 2 )
Given:
- A number of Resistances arranged as shown in the figure .
To Find:
- Equivalent resistance across branch
- R and S
- I and Q
- C and D
- X and Y
Solution:
Let the tip of triangle be imagined as point as M
It is clear that Resistance RM and MS are in series combination
Hence using equation (1)
R(RMS) = R(RM) + R(MS).
R(RMS) = ( 1.5 + 1.5 ) ohm
R(RMS) = 3 ohm
Also equivalent of RMS is in parallel with RS
Hence equivalent resistance between R and S
Using equation (2)
R(RS) = ( 3 x 1.5 )/( 3 + 1.5 )
R(RS) = 1 ohm
______________________________
Resistance in series across XY branch
=> ( 1.5 + 1.5 + 1 + 1.5 + 1.5 ) ohm
=> 7 ohm
and
=> ( 1.5 + 1.5 ) ohm
=> 3 ohm
Equivalent resistance across XY is
R(XY) = ( 7 x 3 )/( 7 + 3 )
R(XY) = 21/10
R(XY) = 2.1 ohm
______________________________
Resistance in series across CD branch is
=> ( 1.5 + 2.1 + 1.5 ) ohm
=> 5.1 ohm
And
=> ( 1.5 + 1.5 + 1.5 ) ohm
=> 4.5 ohm
Hence equivalent resistance across C and D
R(CD) = ( 5.1 x 4.5 )/( 5.1 + 4.5 )
R(CD) = 22.9 / 9.6
R(CD) = 2.39 ohm
______________________________
Equivalent Resistance across I and Q is
R(IQ) = ( 1.5 + 2.39 + 1.5 ) ohm
R(IQ) = 5.39 ohm
______________________________
Q1) Resistance across R and S
Answer : 1 ohm
Q2) Resistance across I and Q
Answer : 5.39 ohm
Q3) Resistance across C and D
Answer : 2.39 ohm
Q4) Resistance across X and Y
Answer : 2.1 ohm