Electrical Engineering - Energy and Power - Discussion

Discussion Forum : Energy and Power - General Questions (Q.No. 1)
1.
A 33 half-watt resistor and a 330 half-watt resistor are connected across a 12 V source. Which one(s) will overheat?
33
330
both resistors
neither resistor
Answer: Option
Explanation:
No answer description is available. Let's discuss.
Discussion:
58 comments Page 2 of 6.

Oorja said:   10 years ago
I agree that the connection is not clear. If connected in series then option D otherwise option A.

Akhil said:   1 decade ago
It should be "B" because in both resisters power is same i.e, 0.5 w.

So 330 R will have high power loss i^2*r than the 33 R.

Pratap Kumar said:   10 years ago
Heat is I^2R. This loss is more in 33 ohm resistor. Option A is correct.

Arun said:   10 years ago
33 ohm will draw more current compared to 330 ohm, since they are connected in parallel 12 remains fixed across both but current gets splitted according to the resistance opposed, obviously 330 will oppose more current hence will dissipate less while 33 will draw in more current thus dissipating heat more, if any mistake please clarify me.

Marshall said:   10 years ago
Both load are resistive components. It dissipate power. For sure both of them will produce heat. So both of them.

Stuti kushwaha said:   10 years ago
Option A should be correct according to i^2r we see that more current flow through 33 ohm. So more heat should across it.

S K Pillai said:   9 years ago
Question should be more clear. Whether the resistances are in series or in parallel? The answer differs D or A.

Sonu kumar said:   9 years ago
Because both the resistor has equal rating and heating of resistor depends on wattage only. Not on the type of connection.

CHAVITINA RAMAKRISHNA said:   9 years ago
Equal rating not given, why you people calling equal rating?

Vikas said:   9 years ago
The value is the maximum wattage the part can dissipate without damage. The value specified is usually at room temp (25C), and the rating will need to be de-rated for higher temperatures.

Some types of resistors may need heatsinking to meet the stated power specs. The large 5, 10, 25, and 50-watt resistors with aluminum cases usually need a fairly large heat sink to achieve their ratings.

So, if P = I^2 * R or P = V^2/R for the resistor in your application is less than the rated power (taking into consideration any derating at higher temps) then your part will be fine.

So, answer A is right one as it was a wrong design by using half a watt 33-ohm resistor this circuit is not right.


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