14.3 Flashcards Preview

A2 Physics > 14.3 > Flashcards

Flashcards in 14.3 Deck (8)
Loading flashcards...
1
Q

What desire was there following the Industrial Revolution?

A

Following the Industrial Revolution there was a desire to make steam engines do as much work possible for fuel burnt.

2
Q

What did James Joule investigate?

A

James Joule compared worked done by an electric battery consuming zinc and a steam engine consuming a pound of coal. Heat was measured by the temperature increase it produced in water.

3
Q

What does one calorie of heat achieve?

A

One calorie of heat will raise temperature of 1kg of water by 1 degree celsius.

4
Q

What was caloric theory? What did Joule show?

A

According to caloric theory heat was conserved but Joule showed that work alone can raise water’s temperature significantly.

5
Q

What is the first law of thermodynamics?

A

Heat and work produce the same effect. For complex systems, internal energy U can’t be found but change in U can and so heat received/energy transferred thermally, Q= W (work done) + change in U (both can be negative if its energy transferred from the system)

6
Q

What is the formula for energy transferred?

A

Change in temperature for a given energy transfer relies on the substance mass and the type of substance.
ENERGY TRANSFERRED = mass of substance * constant for substance * temperature increase
Change in internal energy=mc * change in temperature, where c is a constant (specific thermal capacity) and change in 0 is in degrees.

7
Q

When can ^U=mcT not be used?

A

The equation using specific thermal capacity can’t be used when water is boiled as work is done to break bonds.

8
Q

How can specific thermal capacity of water be found?

A

An immersion heater is connected to an electric circuit and placed in water. For a metal, sample cylinders with a hole the same dimensions as the heater and another for the thermometer may be used. Make appropriate measurements of the water to find the specific thermal capacity. Q must be minimised so U=W.