Electrical Engineering - Energy and Power - Discussion
Discussion Forum : Energy and Power - General Questions (Q.No. 9)
9.
A 120 
resistor must carry a maximum current of 25 mA. Its rating should be at least
resistor must carry a maximum current of 25 mA. Its rating should be at leastDiscussion:
59 comments Page 4 of 6.
Rohit kumar said:
1 decade ago
P = i^2*R.
So that,
P = 25^2*120 = 25*25*120*(10^-3) = 75mW.
But is not exist so that what right answer of that question.
So that,
P = 25^2*120 = 25*25*120*(10^-3) = 75mW.
But is not exist so that what right answer of that question.
Sweta said:
1 decade ago
P = I^2*R.
P = (Imax)^2 * R.
P = (Irms*sqrt(2))^2*R.
P = (0.025*sqrt(2))^2* 120.
P = (0.035355)^2 *120.
P = 150mW.
P = (Imax)^2 * R.
P = (Irms*sqrt(2))^2*R.
P = (0.025*sqrt(2))^2* 120.
P = (0.035355)^2 *120.
P = 150mW.
(1)
R n trimukhe said:
1 decade ago
Simply go through ohms law,
V = IR.
V = 25*10-3*120.
V = 3 v.
P=VI.
P=3*25*10-3.
P=75 mWatt.
V = IR.
V = 25*10-3*120.
V = 3 v.
P=VI.
P=3*25*10-3.
P=75 mWatt.
Rabi Sankar Samanta said:
1 decade ago
p = I2R (25mA=0.025A).
P = 0.025*0.025*120.
P = 0.075W.
P = 75 mW.
Answer did not maching.
P = 0.025*0.025*120.
P = 0.075W.
P = 75 mW.
Answer did not maching.
Biswa Bhusan Pradhan said:
1 decade ago
I think the answer is 75 mW but it is not in d option.
I2R= 0.025*0.025*120 = 75 mW.
I2R= 0.025*0.025*120 = 75 mW.
Mohammed Irshad said:
1 decade ago
Option B is correct.
Explanation:
Rating current value = Irms value.
Maximum current value = Imax value.
Imax = Irms/sqrt(2).
P = Irms^2*R.
= (sqrt(2)*Imax)^2*R.
= 150mA.
Explanation:
Rating current value = Irms value.
Maximum current value = Imax value.
Imax = Irms/sqrt(2).
P = Irms^2*R.
= (sqrt(2)*Imax)^2*R.
= 150mA.
Soumen said:
1 decade ago
P=I^2*R is correct when current passing through it is given but they have given maximum current we known P=VI we known I 25ma. So the answer should be in multiples of 25.
THE MAN said:
1 decade ago
Rating of any device is such that it should carry current up to twice of the capacity. May be this reason so answer is doubled.
Chip Tausch said:
1 decade ago
Here we just need to use P=i^2 R for the power through the resistor, which comes out to 75 mW.
Then I doubled this for derating. 150mW.
Then I doubled this for derating. 150mW.
Chandra sekhar said:
1 decade ago
@Pranav is correct.
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