# 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?

Discussion:

56 comments Page 1 of 6.
Saumya Ranjan senapati said:
2 years ago

There are 32wattt and 330 watts are connected means in series so the current is constant heat depends on current resistance and time here r&t also constant and we know the previous eqÃ± current is also constant so D is the correct answer.

(5)

Kooba said:
4 years ago

The word across means parrallel,

ie. The two resistance are parallel to the voltage (12v) source,

Then, both resistance have 12 volts resistance across then,

Then the power source across 33ohm is using v^2/R = 12^2/33 = 4.36 watts (overheat) ,

With 330 ohm, power = 12*12/330 =0.436 watts (won't over heart).

Therefore, the answer is "A".

ie. The two resistance are parallel to the voltage (12v) source,

Then, both resistance have 12 volts resistance across then,

Then the power source across 33ohm is using v^2/R = 12^2/33 = 4.36 watts (overheat) ,

With 330 ohm, power = 12*12/330 =0.436 watts (won't over heart).

Therefore, the answer is "A".

(12)

Saikiran said:
5 years ago

What is a half watt resistor?

(5)

HAris said:
5 years ago

All.

Here the value of resistances is given just to confuse us, cause.

"The rate at which heat is dissipated is called power" by formula : Power = heat/time.

So power is directly proportional to heat so if power rating is the same of each resistor so heat dissipation will also be the same. So neither of the resistor will be heated up at the power rating of 0.5 watts.

Here the value of resistances is given just to confuse us, cause.

"The rate at which heat is dissipated is called power" by formula : Power = heat/time.

So power is directly proportional to heat so if power rating is the same of each resistor so heat dissipation will also be the same. So neither of the resistor will be heated up at the power rating of 0.5 watts.

(7)

Sunnieth said:
5 years ago

1) What is a half watt resisting?

2) What does it mean to connect resistors across a potential difference

3) What is the influence of series or parallel connection of the resistors themselves in this question?

4) If a half watt is actually 0.5watt fix rating, does the half watt rating cancels out the effect of the nature of resistance arrangement?

2) What does it mean to connect resistors across a potential difference

3) What is the influence of series or parallel connection of the resistors themselves in this question?

4) If a half watt is actually 0.5watt fix rating, does the half watt rating cancels out the effect of the nature of resistance arrangement?

(2)

Vishal said:
6 years ago

Since power is given heat = I^2 x R x t, since I^2 R is the same for both resistors, neither will overheat.

(1)

Junaid Ahmed Hassan said:
6 years ago

By Ohm's law, V=I * R.

Power dissipated across the resistor, P=I^2 x R.

Let R1=33 ohm, R2=330 ohm.

So, let's calculate the current through each resistor. We know V = 12V.

Current through the resistor R1, I(R1)=V/R1= 12/33= 0.36 A.

Power dissipated by R1, P(R1)= I(R1)^2 x R1 = 0.36^2 x 33 = 4.27 Watts.

Current through resistor R2, I(R2)=V/R2=12/330=0.036 A.

Power dissipated by R2, P(R2)= I(R1)^2 x R2= 0.036^2 x 330 = .42 Watts.

Power dissipated across the resistor, P=I^2 x R.

Let R1=33 ohm, R2=330 ohm.

So, let's calculate the current through each resistor. We know V = 12V.

Current through the resistor R1, I(R1)=V/R1= 12/33= 0.36 A.

Power dissipated by R1, P(R1)= I(R1)^2 x R1 = 0.36^2 x 33 = 4.27 Watts.

Current through resistor R2, I(R2)=V/R2=12/330=0.036 A.

Power dissipated by R2, P(R2)= I(R1)^2 x R2= 0.036^2 x 330 = .42 Watts.

(4)

D Shwetha said:
6 years ago

Here, it is given that, the resistors are 0.5W & also a parallel connection.

Heat is directly proportional to power (H=P*t). So, power rating 0.5W & Heat is also both resistors are same.

Heat is directly proportional to power (H=P*t). So, power rating 0.5W & Heat is also both resistors are same.

Sher shah said:
6 years ago

Both the resistors have same power rating so no one will be heat up.

Abdul Ghafoor said:
6 years ago

The heat is cause by current flowing through it so these two resistors are connected in series and current is same across both so neither resistor is overheated because value of current is very less.

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