Voltage Divider

Question 16
I understand that the wiper @25% sets the equivalent resistance of the pot to 1K25Ω . I then used the voltage divider formula and got Vout to equal 4.44V.
However the answer given is 1.29V.

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For this example


We can replace the POT with simply voltage divider:



So in our example we have this situation
Pot is set to 25%. So this means that lower resistance has 1.25K and upper has 5K - 1.25K = 3.75K

So situation look like this



Vout = 10V * 1.25K/5K = 10V * 0.25 = 2.5V

Now if we connect the 1K load resistance to the output terminal of our pot we get this situation:



Vout = 10V * ( R2||Rload ) / ( (R2||Rload) + R1) = 10V * 555Ω/ ( 3.75KΩ + 555Ω ) = 1.289V ≈ 1.29V

Question 18
I'm having trouble calculating the equivalent resistance in this question. I've been scratching my head but I'm finding it hard to get my head around it. Are the two 5K resistors supposed to be added together in series and then, is the 100K in parallel with that?

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Try solve this equivalent circuit