SteamKing said:You don't use units in your calculations, so they're hard to check.
When doing calculations on the rise in temperature of a substance, you want to subtract the colder temp. from the hotter temp.
Which is colder, -30 °C or -10 °C ?
(also, you have a typo in the temperatures used in your calculation of Q.
What is 3.3×105 ? This doesn't seem to be the heat capacity of ice.
The value you've used for the specific heat of ice looks odd to me. Where did it come from and what are the units?MaryBarnes said:Homework Statement
a 0.25 kg piece of ice at -30°C is warmed by an electric heater and the following graph of temperature is produced.
-use the information on the graph to determine the power output of the heater
the graph shows that the ice went from -30degC to -10 degC in 150s
Homework Equations
Q=mcΔt
p=w/Δt
The Attempt at a Solution
Q=mcΔt
=(0.25)(3.3*105)((-30)-(-20))
=82500*(-20)
1.65*106
should this be negative?
You might want to use different variable names for the change in time and change in temperature. It is common to use upper case T for temperatures and lower case t for times.p=w/Δt
=1.65*106/150
=11000
MaryBarnes said:=0.25kg*2100J/(kg °c)*((-10°C) - (-30) °C)
=525*(-20)
=-10500J
P=10500J/150s
=70w
is this ok?
SteamKing said:-10 - (-30) is how much? This is a simple problem in arithmetic.
Just hit the edit button in the lower left hand corner.MaryBarnes said:its 20, but my answer has a negative. i was going to edit it but don't know how to
I see now. Thanks!SteamKing said:Just hit the edit button in the lower left hand corner.
Power output is a measure of the rate at which energy is transferred or converted from one form to another. It is typically measured in watts (W) or kilowatts (kW).
To calculate power output, you need to know the amount of energy transferred or converted and the time it took to do so. The formula for power output is: power output = energy transferred / time.
Power output and power consumption are two related but distinct concepts. Power output refers to the amount of energy that is being transferred or converted, while power consumption refers to the amount of energy being used or consumed. Power output is typically measured in watts or kilowatts, while power consumption is typically measured in kilowatt-hours (kWh).
Power output is a key factor in determining the performance of a system or device. Generally, the higher the power output, the better the performance will be. This is because a higher power output means that energy is being transferred or converted at a faster rate, resulting in more work being done in a given amount of time.
In most cases, it is possible to increase power output by making changes to the system or device. This can be achieved through various methods such as upgrading components, improving efficiency, or increasing the input of energy. However, there may be limitations depending on the specific system or device and its capabilities.