Electrical Engineering - Series-Parallel Circuits - Discussion

@All.

First understand the question.

For voltage divider circuit, V_out=V_in×(R2/(R1+R2)); R2-Load resistance to be changed. If we assume V_in=50V.
For R2=1Mohm, V_out~49V.
For R2=18Kohm, V_out=30V. For R2=12Kohm, V_out=25V.

That's why, 12Kohm resistance has the most reduction in output voltage.

So it affects more. I hope you will understand.

The formula for output voltage is;

V (out) = V (In) [ (RL / (R1 + RL) ]
So, if we take 1M ohm then the result will be V (out) = V (In) (0.9).
And if we take 12k ohm then the result will be V (out) = V (In) (0.33).
So, the output voltage will be more affected if the resistance value will be less so the correct answer is 12k ohm.

Voltage divider means series circuit.

Nice explanation @Vekatesh.

The simple thing is both resistor has same value 12k, so both resistors have the same effect.

Sereis = 12 + 12 = 24, that is 24/2 = 12ohm.

To get more voltage at the output, circuit resistance must be low, low resistance means low voltage drop then more output voltage.

Now consider 1M resistor is connected across 12k then total resistance become 11.85K.

Now consider 24K resistor is connected across 12k then total resistance become 8K.

Now consider 18k resistor is connected across 12k then total resistance become 7.2k.

Now consider 12k resistor is connected across 12k then total resistance become 6k.

So out of 8k, 11.85K, 7.2K and 6K, the voltage across 6k is small.

So this resistor reduces the output voltage. So 12k resistor have the more effect on output voltage.

The load resistor is connected across any one 12k resistor.

Now consider 1M resistor is connected across 12k then total resistance become 8K.
Now consider 24K resistor is connected across 12k then total resistance become 11.85k.
Now consider 18k resistor is connected across 12k then total resistance become 7.2k.
Now consider 12k resistor is connected across 12k then total resistance become 6k.

So out of 8k, 11.85K, 7.2K and 6K, the voltage across 6k is small.

So this resistor reduces the output voltage. So 12k resistor have the more effect on output voltage.

If we connect 12k load resistor then output voltage reduces to low value, compared to other load resistance value.

The correct answer is D.

The answer cannot be A or C, because they given that two 12k resistors are in series, so 1M and 18K doesn't come into picture.

Now the answer may be 12K or 24K.

A voltage divider circuit must contain at-least two loads and we should take output across any one load. If we take voltage across total load then it is not called a voltage divider circuit.

So in this problem we should take voltage across any 1 12K resistor. Hence 12k resistor only can have effect on output voltage.