Examveda

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.

This Question Belongs to Electrical Engineering >> Energy And Power

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Comments (2)

  1. Sohail Abbasi
    Sohail Abbasi:
    4 months ago

    correction please : as P=i^2*R = ((.025)^2 * 120 = 0.075 w

  2. IHTISHAM UL
    IHTISHAM UL:
    2 years ago

    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

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