Electrical Engineering - Series-Parallel Circuits - Discussion

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 1k ohm then the result will be V (out) = V (In) (0.25).
So, the output voltage will be less affected if the resistance value will be more so the correct answer is 1M ohm.

The question is pertaining to Voltage Divider, hence: V(output) = V(input) * (R1 / (R1 + R2))
Since the question is the LEAST effect of the Output Voltage we can then assume any value for V(input) in the example below I used 5 Volts, R1 or R (load) is connected parallel to the 3 series resistor because that is how voltage divider works and example would be like this.

V (out) = 5V * (1M ohms / (3K ohms + 1M ohms) = the answer would be appromately equal to 5, since the output and input are almost of equal value then R (load) which is 1 M ohms has the LEAST effect on the circuit.

The Circuit has three 1 K ohms in series & load resistor also.

Question is which of the following load resistors will have the least effect on the output voltage?

330 ohms will have the least effect on voltage across 1 K ohms.

R1= 3(1k ohm) = 3k ohm.

Vout = (R2/(R1+R2))Vin.

Lets take minimum resistor R2 = 330 ohm.

Vout = (R2/(R1+R2))Vin.
Vout = (330/3330)Vin.
Vout = 0.099 Vin.

Lets take maximum resistor R2 = 1M ohm.

Vout = (R2/(R1+R2))Vin.
Vout = (1M/1003000)Vin.
Vout = 0.997 Vin.

Here you can observe, bigger the value of R2, smaller the effect on Vout. So, the answer is 1M ohm.

The question is when you connect which value of the following resistor the value of output voltage doesn't alter a lot.

Out of the four 1 M is the high value of load resistance which is equal to open circuit when compared to other.

@Siva.

How it's possible 1.1/(1+1) = 1?

As the question is that among the options which has least effect on output voltage. As all option except 1M is less than or equal to 1K so the output of voltage divider has the effect on other 3 loads except 1M because for a high value load resistance the current for specified voltage will be low as compared to low load. So 1M will be effected least.

Voltage drop is directly related to resistance.

Higher the resistance higher will be the voltage drop.

Voltage drops across internal resistances of the source, across conductors, across contacts, and across connectors are undesired; as supplied energy is lost (i.e. dissipated).

Voltage drops across loads are desired; as supplied energy performs useful work.

Hence in the above question the supplied energy will be put to maximum use when the value of load resistance is maximum.

As the question is asked for load resistance the answer will be 1M ohm.

If the question would have been for internal resistance then the answer would have been 330 ohm.

Please give me the correct solution for this one.

The effect of load on terminal voltage depends on load resistance, if the load resistance is less than current drawn by the load will be more hence terminal voltage drop is more.

Hence, most resistance load will have less effect on voltage.