## aminamoazzam one year ago Need Help in MCQ's see attachment .. Plzz help ..

1. aminamoazzam

These are the questions Ans for 27 is D Ans for Q 28 is A and for 38 is C

2. aminamoazzam

@Michele_Laino

3. aminamoazzam

@ganeshie8

4. Michele_Laino

question #28 field line has to be perpendicular with respect to the surface of the conductors

5. Michele_Laino

@aminamoazzam

6. Michele_Laino

so pictures B and D can be excluded

7. Michele_Laino

we can exclude also picture C, since the charge density is greater when the distance between metal plates is smaller. so the right answer is option A

8. aminamoazzam

thanks .. can u help by explainingg the rest of questions

9. Michele_Laino

question #36 before removing the resistor W, your circuit is: |dw:1433879076085:dw|

10. Michele_Laino

and its equivalent circuit is: |dw:1433879222031:dw|

11. Michele_Laino

now the current is: I = V/R

12. Michele_Laino

|dw:1433879314684:dw|

13. Michele_Laino

acros each pair of resistor, there is a voltage drop of $\frac{R}{2}I = \frac{R}{2} \times \frac{V}{R} = \frac{V}{2}$

14. Michele_Laino

and the dissipated powers by the resistors are all equals each other, and they are equal to: $P = \frac{{{V^2}}}{{4R}}$

15. Michele_Laino

now after rimotion of the resistor W, your circuit becomes: |dw:1433879696882:dw| and its equivalent circuit is: |dw:1433879758406:dw|

16. Michele_Laino

the current is: I=2V/3R power dissipated by resistor X is: ${P_X} = R{I^2} = R{\left( {\frac{{2V}}{{3R}}} \right)^2} = \frac{{4{V^2}}}{{9R}}$

17. Michele_Laino

voltage drop across Y and Z resistors is: ${V_{YZ}} = V - \frac{{2V}}{3} = \frac{V}{3}$

18. Michele_Laino

power dissipated by each resistor Y and Z is: ${P_Y} = {P_Z} = \frac{1}{2}\left( {\frac{{{V^2}}}{R} - \frac{{4{V^2}}}{{9R}}} \right) = \frac{5}{{18}}\frac{{{V^2}}}{R}$

19. Michele_Laino

reassuming: before rimotion of X resistor we have: power dissipated by each resistor $P = \frac{{{V^2}}}{{4R}}$

20. Michele_Laino

oops. rimotion of W-resistor after rimotion of the W-resistor, we have: power dissipated by the X-resistor: ${P_X} = \frac{{4{V^2}}}{{9R}}$ power dissipated by the Y-Z resistors, separately: ${P_Y} = {P_Z} = \frac{5}{{18}}\frac{{{V^2}}}{R}$

21. Michele_Laino

what can you conclude?

22. Michele_Laino

Qustion #27 I'm sorry, I'm not good with diffraction gratings

23. aminamoazzam

@Michele_Laino Thanks ur explanation really helped me .. i understood both of the questions u explained ..

24. Michele_Laino

:)