A 120 Ω resistor must carry a maximum current of 25 mA. Its rating should be at least
A. 4.8 W
B. 150 mW
C. 75 mW
D. 480 mW
Answer: Option C
Solution (By Examveda Team)
We need to find the power rating of the resistor.The formula we'll use is: P = I2R, where:
* P is the power (in Watts)
* I is the current (in Amperes)
* R is the resistance (in Ohms)
First, convert the current from milliamperes (mA) to amperes (A):
25 mA = 25 / 1000 A = 0.025 A
Now, plug the values into the formula:
P = (0.025 A)2 * 120 Ω
P = 0.000625 * 120 W
P = 0.075 W
Convert Watts(W) to milliWatts(mW):
0. 075 W = 0.075 * 1000 mW = 75 mW
So, the resistor rating should be at least 75 mW.
correction please : as P=i^2*R = ((.025)^2 * 120 = 0.075 w
One formula for power is I squared times R.
P = 0.025A^2 x 120 ohms = 0.075W or 75mW
So a resistor rated at least double that. 150mW