Direct Current QA 14
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The document discusses a problem involving two wires (ab and bc) made of the same material and connected in parallel, analyzing parameters like voltage, power, current density, and electric field. It concludes that the potential difference across bc is twice that across ab, and the power dissipated in bc is four times that in ab. The correct option regarding these relationships is determined to be (b).
![Physics Helpline
L K Satapathy
Direct Current - 14
Cells in Parallel
CONCEPTS
In SERIES , currents through both resistors are same
POWER Dissipated 2
.P I R P R
Potential Difference .V I R V R
Resistance
2 2
. . 1
.
L L
R R
A r r
Current Density
2 2
1
.
I I
J J
A r r
Electric field
V
E E V
L
2R1R
V
2P1P
2V1V
I
[ I = const.]
[ I = const.]
[ I = const.]
[ L = const.]
[ L = const.]](https://image.slidesharecdn.com/directcurrent14-160626113915/85/Direct-Current-QA-14-3-320.jpg)
Direct Current QA 14
- 1. Physics Helpline L K Satapathy Direct Current - 14 Voltage / Current Density Power / Electric Field Comparison of
- 2. Physics Helpline L K Satapathy Direct Current - 14 Cells in Parallel Question : Two wires AB and BC, each of length L , and made of the same material are joined together as shown in the figure. (a) PD across BC is twice that across AB (b) Power dissipated in BC is four times that in AB (c) Current densities in AB and BC are equal (d) Electric field inside AB and BC are equal A B C L L I The radius of wire AB is twice the radius of wire BC. If current I flows through the composite wire , then
- 3. Physics Helpline L K Satapathy Direct Current - 14 Cells in Parallel CONCEPTS In SERIES , currents through both resistors are same POWER Dissipated 2 .P I R P R Potential Difference .V I R V R Resistance 2 2 . . 1 . L L R R A r r Current Density 2 2 1 . I I J J A r r Electric field V E E V L 2R1R V 2P1P 2V1V I [ I = const.] [ I = const.] [ I = const.] [ L = const.] [ L = const.]
- 4. Physics Helpline L K Satapathy Direct Current - 14 Cells in Parallel Given : Wires AB and BC are made of same material 1 2 Radius of AB = 2 (Radius of BC) 1 22r r Area of cross section of AB = 4(Area of cross section of BC) 1 24A A Lengths of AB and BC are equal 1 2L L L Resistances 2 21 1 2 1 2 1 . . 1 4 ARL L R and R A A R A A B C L L I
- 5. Physics Helpline L K Satapathy Direct Current - 14 Cells in Parallel (d) E inside AB and BC are equal (a) P D across BC is twice across AB (b) Power in BC is four times that in AB (c) J in AB and BC are equal 1 1 2 1 2 2 1 4 4 V R V V V R 1 1 2 1 2 2 1 4 4 P R P P P R 1 2 2 1 2 1 1 4 4 J A J J J A 1 1 2 1 2 2 1 4 4 E V E E E V Correct option = (b) Answer : We test the options for correctness
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