Calculate percentage change in heat output

AI Thread Summary
To calculate the percentage drop in heat output of a 500W heating unit when the voltage decreases from 115V to 110V, first determine the resistance using the formula R=V^2/P. After finding the resistance, apply the new voltage of 110V to calculate the new power output. The percentage change in heat output can be calculated using the formula %=(initial-final)*100/initial. The final answer obtained is an 8.5% decrease in heat output. The discussion also touches on opinions regarding online exam solutions.
physicist93
Messages
11
Reaction score
0

Homework Statement


A 500W heating unit is designed to operate on a 115V line. If the line voltage drops to 110V, calculate the percentage drop in heat output.

Homework Equations


R=V^2/P

The Attempt at a Solution


P=V^2/R

Use V=115, then use V=110, use Power P=500...but not sure how

p.s. I am a UK Physics student. I was wondering could you also say whether you are in the UK or US or...
 
Last edited:
Physics news on Phys.org
Find the resistance of the heater. Use that value of resistance and 110 volts to find new power output. %=(initial-finial)*100/initial
 
Thanks that's great! I've done it now
 
I got an answer of 8.5%! sounds right...

Btw what do people think about the questions on online-exam-solutions?
 

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 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'

Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'

Figure 1 Overall Structure Diagram Figure 2: Top view of the piston when it is cylindrical A circular opening is created at a height of 5 meters above the water surface. Inside this opening is a sleeve-type piston with a cross-sectional area of 1 square meter. The piston is pulled to the right at a constant speed. The pulling force is（Figure 2）： F = ρshg = 1000 × 1 × 5 × 10 = 50,000 N. Figure 3: Modifying the structure to incorporate a fixed internal piston When I modify the piston...
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

Power output of a intercooler and turbocharger
Replies
1
Views
2K
Long distance electrical transmission efficiency
Replies
2
Views
2K
Change in temperature of air in a closed system
Replies
16
Views
2K
Heating Effect of Electric Current-Transmit at High Voltage
Replies
5
Views
2K
Why does having a high input impedance and low output impeda
Replies
4
Views
2K
Calculating Heat Loss in a Series Circuit
Replies
5
Views
4K
A circuit involving two non-linear resistances (incandescent lamps)
Replies
14
Views
2K
Carbon Dioxide Output Percentage Change
Replies
1
Views
2K
What is the change in internal energy after two processes?
Replies
10
Views
2K
Current and resistance of wire heating up water
Replies
4
Views
4K

Hot Threads

Recent Insights

Back
Top