A component with a 39 Ohm resistor is rated for use at power levels not exceedin

Question

A component with a 39 Ohm resistor is rated for use at power levels not exceeding 1,024 mW. How much current can safely flow through the component? Express the answer with two decimal places (even if the rounded number will be larger than the value of the safe current).

A 76 W light bulb with a resistance of 177 is connected to a power supply with a 119 V. What is the internal resistance of the power supply? Express the answer with one decimal place.

A power supply with internal resistance of 3 applies a voltage of 18 V. If a load resistor of 34 is in series with the power supply, then what is the current going through the circuit? Express the answer with two decimal places.

Explanation / Answer

1.
use:
P= i^2 * R
1024*10^-3 W = i^2 * 39 ohm
i = 0.16 A
Answer:0.16 A

2.
Let internal resistance be r
Then net resistance, R' = 177+r ohm
use:
P= V^2 / R'
76 = 119^2 /(177+r)
13452 + 76r = 14161
r=9.33 ohm
Answer:9.3 ohm

3.
Net resiatnce, R' = 3 + 34 = 37 ohm
use:
V=I*R'
18 = I*37
I=0.49 A
Answer: 0.49 A

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