physxx mcq.

[hassam]

 

[hassam]

well......is the way i will use below correct or not........
since I is same throughout so ratio of resistance is equal to ratio of P.D across the particular resistors....
for an output 3V this means p.d across R1 is 2 V.check option C...R1/(R2+R3)=P.D Across R1 tht is 2 divided by P.D across R2 and R3 i.e 3......both ratios are same........i want this assurance that is P.D across R2 2V when output is 3V or hav i reversed it up...pls clear this thing to me

 

[DragonCub]

The three resistors are in series, so the total 5V p.d. is divided by them.
Here we can simply get the p.d. across R3 = +2V - 0V = 2V
p.d. across R2 = +3V - +2V = 1V
and thus calculate the p.d. across R1 = +5V +3V = 2V
p.d. ratio R1 : R2 : R3 = 2:1:2
Then it is easy to get the answer: C.

 

[hassam]

 

[DragonCub]

Simply regard the XY as a resistor, in parallel with the variable one.
When the R of the variable resistor increases, the XY wire gets lower p.d.
And to maintain the p.d. across XN, point N should move to the right to gain voltage.
Answer is D.

 

[hassam]

i dint understand why it shud Be nearer to Y