Find the resistance of the coil

  • Thread starter Thread starter Cisneros778
  • Start date Start date
  • Tags Tags
    Coil Resistance
AI Thread Summary
To find the resistance of the coil in the water heater, the key is to calculate the energy required to heat 270 mL of water from 20°C to boiling point. The power can be determined using the formula for thermal energy, Q = mc*dT, where m is the mass of the water, c is the specific heat capacity, and dT is the temperature change. Once the power (in watts) is known, it can be related to the voltage and current using the formula P = V * I. Finally, resistance can be calculated using R = V/I, where V is the voltage of the power supply. This approach effectively combines thermal energy concepts with electrical formulas to solve for the coil's resistance.
Cisneros778
Messages
48
Reaction score
0

Homework Statement


A water heater consisting of a metal coil that is connected across the terminals of a 24-V power supply is able to heat 270 mL of water from room temperature (20°C) to boiling point in 70 s. What is the resistance of the coil? (When entering units, use ohm for Ω.)


Homework Equations


R = dV/I


The Attempt at a Solution


I am not sure how to approach this one. I think the temperature is throwing me off. I have V so I am trying to find I. I was thinking of using I = dQ/dT since I have the time interval, but finding Q isn't possible unless I am given values for charges. I almost want to use Q = mc*dT but Q here is thermal energy so I'm back to square one.
 
Physics news on Phys.org
Your thought about thermal energy looks promising. How much energy is required to heat the given amount of water by the stated amount? If it's done in the stated amount of time, what's the power (watts) involved?
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

Temperature dependence of resistance
Replies
6
Views
890
A Galvanometer of Coil Resistance 50 Ω Deflects Full Scale....
Replies
2
Views
2K
Calculating Heat Generated in a Coil due to Changing Current and Resistance
Replies
22
Views
6K
Electric current and resistance question
Replies
2
Views
2K
Long distance electrical transmission efficiency
Replies
2
Views
2K
Calculating Induced Current in a Coil Surrounding a Changing Current Solenoid
Replies
5
Views
4K
Coils arrangement so the hotplate operates at 3 diff. powers
Replies
25
Views
3K
Voltage in secondary coil of transformer
Replies
13
Views
3K
Engineering Finding the Armature Resistance from winding/coil resistance
Replies
1
Views
2K
What charge circulates through the coil?
Replies
17
Views
2K

Hot Threads

Recent Insights

Back
Top