Question

8. A voltage of 200V is applied to a tapped resistor of 500 ohm. Find the resistance
between two tapping points connected to a circuit needing 0.1A at 25V. Calculate
the total power consumed.
89ohm, 93.5W
39ohm, 63.5W
79ohm, 83.5W
49 ohm,83.5W​

Answer 1

Answer:

option(c) 79 ohm,83.5W

Explanation:

Let R1 = top portion of 500 Ohm resistor

Let R2 = bottom portion of 500 Ohm resistor = (500 Ohm - R1)

I of R1 = 175V/R1 = 25V/R2 + .1A

So,

175/R1 = 25/(500 - R1)

(175/R1) - [25/(500 - R1)] = 0

.1R1^2 - 250R1 + 87,500 = 0

R1 = 420.844 or 2079.156 Ohms but R1 must be less than 500 Ohms so R1 = 420.844 Ohms

R2 = (500 - 420.844)Ohms = 79.156 Ohms

R2 ll RL = 79.156 ll 250 = 60.12 Ohms

Total power consumed = V^2/Total resistance =[(200V^2) / (420.844 + 60.12)Ohm = 83.17 Watts