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.
Sathish said:
1 decade ago
They are not that one is RMS value its 75 mW only.
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.
Ashish said:
10 years ago
How answer is 150?
Prasad said:
10 years ago
Rating of resistor = 2VI.
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.
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.
Rkn said:
10 years ago
How could 150mW be correct answer. It is clear from the question that for a power rating beyond 75mW the resistor's characteristics will be altered.
So the maximum rating is 75mW and among options only 15mW is less than this value. So the answer should be 15mW. Anyway a 20W rated doesn't burn out at this value.
So the maximum rating is 75mW and among options only 15mW is less than this value. So the answer should be 15mW. Anyway a 20W rated doesn't burn out at this value.
PRITAM said:
10 years ago
The answer should be 75 mw because which is not in option. Some of guys have said that it will be 150 mw. How if you really did then I think you must solved after seeing an option?
Stuti kushwaha said:
10 years ago
Irms = 25.
Im = (25*1.414)^2*12 = 150 mA.
Im = (25*1.414)^2*12 = 150 mA.
Ravindranarayan said:
9 years ago
Yes, 75mw is the correct answer.
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