circuit with 2 voltage sources?

Question

i'm not understanding this question. i don't know how to handle a circuit with 2 voltage sources

an electric heater is connected to a constant 250V source and absorbs 1000W. Subsequently, this heater is connected to a constant 210V source. What power does it absorb from 210V source? What is the resistance of the heater? Model the electric heater as a resistor.

Answer 1

from P = (V^2)/R

you could solve for the resistance:
R=(V^2)/P
=(250^2)/1000W
= 62.5 ohms

power @ 210V source
P = (V^2)/R
=(210^2)/(62.5)
=705.6W

Answer 2

P = VI
1000 = (250)I
I = 1000/250
I = 4A

R = V/ I
R = 250 / 4
R = 62∙5 Ω

Power @ 210V source;
P = V²/R
=(210²)/(62.5)
=705.6W

Answer 3

Actually, it's 2 different circuits with different supply voltages.
For the 250V circuit
P=E²/R so R=E²/P = 250²/1000 = 62.5 Ω.
Then for the 219V circuit
P=210²/62.5 = 705.6 W

Kewl?

Doug

Answer 4

If it is a 1000 watt heater as you have described, it will draw 1000 watts regardless of the voltage supplied to it. Watts are calculated by multiplying the volts X amps. Therefore the 1000w heater at 250 volts would draw 4 amps of current, while at 210 volts, it would draw 4.76 amps. If you had large enough wire and power supply to carry the load, a 1000 watt heater at 12 volts would draw 83.33 amps.