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 2 of 6.
Sharmila said:
9 years ago
150mw is wrong answer.
Because the given current is in maximum value, how you can multiple with root 2?
The formula is v (r.m.s) = [v(max.)/root 2]. So,the answer is 75mw.
Because the given current is in maximum value, how you can multiple with root 2?
The formula is v (r.m.s) = [v(max.)/root 2]. So,the answer is 75mw.
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.
OMVEER SINGH said:
10 years ago
Max. current always Taking in RMS Value. So we solve this query by Rms value Imax = Square root*Irms.
Then P = I*I*R.
= 25*1.414*25*1.414*120.
= 150 MW.
Then P = I*I*R.
= 25*1.414*25*1.414*120.
= 150 MW.
Richa said:
1 decade ago
I^2*R=25*25*120*(10^-3)^2= 750mW
while this option is not available in the option.. and these are given.. please give me ful explanantion of this question
while this option is not available in the option.. and these are given.. please give me ful explanantion of this question
Rishipal said:
8 years ago
D is correct because maximum current is given it is not RMS current so, it changes in RMS current.
RMS current=maximum current/root2. Then power = i2r.
RMS current=maximum current/root2. Then power = i2r.
Hemant said:
9 years ago
Rated value means the device should operate that value. Here, 75mW is the right answer. We can't say the rated value is 150mW as per the formula.
Sandy said:
1 decade ago
Current = 25 ma = 0. 025 a.
Voltage = ?
Resistor = 120 ohm.
I = v/r.
v = ir.
v = 0.025*120 = 3 v.
p = vi.
p = 3*0.025 = 0.075 w = 75 mw.
Voltage = ?
Resistor = 120 ohm.
I = v/r.
v = ir.
v = 0.025*120 = 3 v.
p = vi.
p = 3*0.025 = 0.075 w = 75 mw.
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.
Yogesh meena said:
6 years ago
The given current value is in rms.
Then the average value will be √(2)*i.
So, P=[√(2)*i]^2*r,
=[1.414*25]^2*120.
=150mW.
Then the average value will be √(2)*i.
So, P=[√(2)*i]^2*r,
=[1.414*25]^2*120.
=150mW.
(2)
Ravi said:
10 years ago
Formula:
Irms = Im\root2 then Im = Ir*root2.
Im value is = 25 mA*root2 = 0.03536 A.
Then P = I*I*R = 0.03536*0.03536*120 = 150 mW.
Irms = Im\root2 then Im = Ir*root2.
Im value is = 25 mA*root2 = 0.03536 A.
Then P = I*I*R = 0.03536*0.03536*120 = 150 mW.
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