Question

Determine the resistance and the

Power Consumption of a resistor
that must be placed in Series
with a 75 ohms resistor across 120 voltage
Sources In other to limit the power
Consumption in the 75 ohms resistor to
90 watt​

Answer 1

34.54 ohms

Step-by-step explanation:

Let the resistance of the new resistor be y.. Thus, total resistance = 75 + y

Now, across voltage of 120 V, current is;

I = 120/(75 + y)

Formula for power is;

P = I²R

Thus, power across 75 ohms resistor which is 90 watts is expressed as;

90 = (120/(75 + y))² × 75

90/75 = 120²/(75 + y)²

(75 + y)² = 120² × 75/90

y + 75 = √12000

y = (√12000) - 75

y = 34.54 ohms