What is the difference between an open system and a closed system in thermodynamics?

In an open system , gas or vapour can flow into and out of the region, for example gas escaping through the nozzle of an aerosol can. In a closed system , the gas remains within the region, although the boundary can expand or contract, for example gas in a piston.

State the sign convention for Q , ΔU and W in the first law of thermodynamics.

Q is positive if heat energy is added, negative if removed ΔU is positive if internal energy increases, negative if it decreases W is positive if work is done by the gas (expansion), negative if work is done on the gas (compression)

The work done, W , is positive if work is done .......... the gas, and negative if work is done .......... the gas.

The work done, W , is positive if work is done by the gas, and negative if work is done on the gas.

True or False? A gas expanding through the nozzle of an aerosol can is an example of a closed system.

False. This is an example of an open system , because gas flows out of the region. A closed system keeps the gas within the boundary, such as gas expanding in a piston.

To what principle is the first law of thermodynamics linked, and to what situations does it apply?

It is based on the conservation of energy , and applies to heating, cooling and work done in all situations, not just to gases.

What does the area under a p-V diagram represent?

The work done by or on the gas.

When a gas expands at constant pressure, is the work done positive or negative, and why?

Positive. The volume increases (+Δ V ) and work is done by the gas (+ W ).

When a gas is compressed at constant pressure, is the work done positive or negative, and why?

Negative. The volume decreases (−Δ V ) and work is done on the gas (− W ).

True or False? The area under a p-V diagram only gives the work done when the pressure is constant.

False. The area under a p-V diagram gives the work done even when both the pressure and volume change during the process, not only when pressure is constant.

In an adiabatic process, all the work done is at the expense of the system's .......... , so the process is usually accompanied by a change in .......... .

In an adiabatic process, all the work done is at the expense of the system's internal energy , so the process is usually accompanied by a change in temperature .

Define the four-stroke petrol engine cycle .

An internal combustion engine cycle that burns fuel once every four strokes of the piston (induction, compression, power, exhaust), requiring two revolutions of the crankshaft. It is also known as the Otto cycle .

Describe what happens during the induction stroke of a petrol engine.

The piston moves down the cylinder, increasing the volume. A petrol-air mixture is drawn in through the inlet valve, at a pressure just below atmospheric pressure.

Describe what happens during the compression stroke of a petrol engine.

The inlet valve closes and the piston moves up, doing work on the gas adiabatically . Near the end of the stroke, the petrol-air mixture is ignited by a spark, causing pressure and temperature to rise rapidly at almost constant volume.

On the theoretical indicator diagram for a petrol engine, what happens between points B and C ?

Heat is supplied and the volume is kept constant; this is when ignition by the spark occurs.

On the actual indicator diagram, the corners of the graph are .......... because the valves take a finite time to .......... .

On the actual indicator diagram, the corners of the graph are rounded because the valves take a finite time to open and close .

Give two reasons why the area enclosed by the actual indicator diagram is smaller than the theoretical diagram.

The expansion and compression are not perfectly adiabatic, so heat transfer occurs The heating and cooling cannot occur at truly constant volume Some exhaust gas or unburnt fuel vapour may be present, not pure air

True or False? A four-stroke petrol engine cycle requires only one revolution of the crankshaft to complete.

False. A full four-stroke cycle requires two revolutions of the crankshaft.

What is drawn into the cylinder during the induction stroke of a diesel engine, and how does this differ from a petrol engine?

Only air is drawn in, compared to a petrol-air mixture in a petrol engine, so there is no fuel present in the cylinder during compression.

How is the diesel fuel ignited in a diesel engine?

During compression, the air reaches a high enough temperature and pressure to vapourise and ignite the diesel fuel, which is injected directly into the cylinder as a fine spray through an injector (no spark plug is used).

On the theoretical indicator diagram for a diesel engine, what happens between points B and C ?

Heat is supplied while the pressure is kept constant, unlike the petrol engine cycle, where heating occurs at constant volume.

The biggest difference between the actual and theoretical diesel indicator diagrams is that from B to C, there is no .......... at the start of the expansion stroke.

The biggest difference between the actual and theoretical diesel indicator diagrams is that from B to C, there is no sharp peak at the start of the expansion stroke.

True or False? The compression stroke (A to B) in the diesel engine cycle occurs at constant pressure.

False. The compression stroke is adiabatic , not constant pressure; both the pressure and temperature of the air increase from A to B.

What happens between points D and A on the diesel engine indicator diagram?

The system is cooled at constant volume .

Why do diesel engines require a higher compression ratio than petrol engines?

To raise the pressure and temperature of the air high enough for the diesel fuel to self-ignite without a spark.

What is pre-ignition , and what can cause it in a petrol engine?

Pre-ignition is when the petrol-air mixture self-ignites before the spark. It can be caused by a compression ratio that is too high, or by a build-up of carbon in the cylinder.

State two disadvantages of a diesel engine compared to a petrol engine.

Diesel engines operate at higher working pressures , making them more expensive to produce as they must be more robust and stable They have a lower power-to-weight ratio

A diesel engine typically has a compression ratio of around .......... , while a petrol engine has a compression ratio of around .......... .

A diesel engine typically has a compression ratio of around 16 , while a petrol engine has a compression ratio of around 10 .

True or False? Diesel engines produce more carbon monoxide, hydrocarbons and carbon dioxide than petrol engines.

False. Petrol engines produce more of these pollutants than diesel engines. A catalytic converter can reduce these emissions, though not below diesel engine levels.

Define calorific value .

The calorific value of a fuel is the amount of energy the fuel stores per unit volume (or per unit mass).

True or False? The brake power of an engine is always greater than its indicated power.

False. The brake power is lower than the indicated power, because some of the indicated power is lost overcoming friction within the engine.

Define overall efficiency of an engine.

Overall efficiency is the ratio of brake power to input power . It is also the product of the thermal efficiency and the mechanical efficiency .

Define thermal efficiency of an engine.

Thermal efficiency is the ratio of indicated power to input power . It shows how well the engine transforms the chemical energy in the fuel into useful power in the engine cylinders.

Define mechanical efficiency of an engine.

Mechanical efficiency is the ratio of brake power to indicated power . It depends on the amount of energy lost to friction in the moving parts of the engine.

How is the overall efficiency of an engine related to its thermal and mechanical efficiencies?

Overall efficiency = thermal efficiency × mechanical efficiency .

Mechanical efficiency depends on the amount of energy lost due to .......... of the engine, caused by friction.

Mechanical efficiency depends on the amount of energy lost due to moving parts of the engine, caused by friction.

True or False? Thermal efficiency is calculated as brake power divided by input power.

False. That ratio is the overall efficiency . Thermal efficiency is the ratio of indicated power to input power .

Define the source in a heat engine.

The source is a high-temperature reservoir at temperature T H , which supplies heat energy Q H to the engine.

Define the sink in a heat engine.

The sink is a low-temperature reservoir at temperature T C , which receives heat energy Q C from the engine.

State the second law of thermodynamics in terms of extracting energy from a heat reservoir.

When extracting energy from a heat reservoir, it is impossible to convert it all into work. Equivalently, thermal energy cannot spontaneously transfer from a region of lower temperature to a region of higher temperature.

Why is it impossible for a heat engine to operate on the First Law of Thermodynamics alone?

If the engine reached the temperature of the source , no heat would flow because they would have reached thermal equilibrium , so no work would be done.

Heat engines convert thermal energy into .......... work, whereas heat pumps transfer heat energy from a low to a high temperature.

Heat engines convert thermal energy into mechanical work, whereas heat pumps transfer heat energy from a low to a high temperature.

True or False? A heat engine that obeyed only the First Law of Thermodynamics, with no friction, would be 100% efficient.

True. Such an engine would be 100% efficient in principle, but it cannot be built in reality because real engines always have frictional losses and so must also obey the Second Law .

Why can the efficiency of a heat engine never be 100%?

Because no heat engine can completely convert heat into work — some heat energy is always lost to the surroundings.

How should the source and sink temperatures be chosen to make an engine as efficient as possible?

The source temperature should be as high as possible and the sink temperature should be as low as possible.

The maximum theoretical efficiency of a heat engine is 100% only if the sink temperature is at .......... .

The maximum theoretical efficiency of a heat engine is 100% only if the sink temperature is at 0 K .

True or False? The maximum theoretical efficiency equation only applies to engines using a specific p - V cycle.

False. This equation is valid for all idealised reversible engines , irrespective of the particular cycle or working substance.

Give three reasons why practical heat engines have a much lower efficiency than their theoretical equivalent.

Any three from: Friction between moving parts, and heat lost through the cylinder walls Incomplete combustion of the fuel, so the temperature rise is lower than expected Power used to drive internal components such as pumps and motors The working gas is not an ideal gas The engine cycle processes are irreversible

Define imperfect combustion as a limitation of a real heat engine.

Heat energy is taken in and rejected over a range of temperatures, rather than entirely at the single temperatures T H and T C , so the maximum temperature is not always reached.

Why do the irreversible processes in a real engine cycle reduce its efficiency?

Energy is dissipated out of the system and there is no equilibrium with the surroundings, as the processes happen too quickly (for example, the valves take a finite time to open and close, and the strokes are not truly adiabatic).

A LevelPhysicsAQAFlashcardsEngineering PhysicsThermodynamics & Engines

Thermodynamics & Engines (AQA A Level Physics): Flashcards

Exam code: 7408

1/85

0Still learning

Know0

FrontThe First Law of Thermodynamics
Define the first law of thermodynamics.
FrontThe First Law of Thermodynamics
State the sign convention for Q, ΔU and W in the first law of thermodynamics.
BackThe First Law of Thermodynamics
Q is positive if heat energy is added, negative if removed
ΔU is positive if internal energy increases, negative if it decreases
W is positive if work is done by the gas (expansion), negative if work is done on the gas (compression)

Was this flashcard helpful?

Cards in this collection (85)

Define the first law of thermodynamics.
The first law of thermodynamics states that $Q = Δ U + W$ , where Q is the energy supplied to the system by heating, ΔU is the increase in internal energy and W is the work done by the system. It is based on the conservation of energy.
What is the difference between an open system and a closed system in thermodynamics?
In an open system, gas or vapour can flow into and out of the region, for example gas escaping through the nozzle of an aerosol can. In a closed system, the gas remains within the region, although the boundary can expand or contract, for example gas in a piston.
State the sign convention for Q, ΔU and W in the first law of thermodynamics.
- Q is positive if heat energy is added, negative if removed
- ΔU is positive if internal energy increases, negative if it decreases
- W is positive if work is done by the gas (expansion), negative if work is done on the gas (compression)
The work done, W, is positive if work is done .......... the gas, and negative if work is done .......... the gas.
The work done, W, is positive if work is done by the gas, and negative if work is done on the gas.
True or False?
A gas expanding through the nozzle of an aerosol can is an example of a closed system.
False.
This is an example of an open system, because gas flows out of the region. A closed system keeps the gas within the boundary, such as gas expanding in a piston.
To what principle is the first law of thermodynamics linked, and to what situations does it apply?
It is based on the conservation of energy, and applies to heating, cooling and work done in all situations, not just to gases.
Define the work done by a gas at constant pressure.
$W = p Δ V$
where W is work done (J), p is the pressure of the gas (Pa) and ΔV is the change in volume of the gas (m³).
What does the area under a p-V diagram represent?
The work done by or on the gas.
When a gas expands at constant pressure, is the work done positive or negative, and why?
Positive. The volume increases (+ΔV) and work is done by the gas (+W).
When a gas is compressed at constant pressure, is the work done positive or negative, and why?
Negative. The volume decreases (−ΔV) and work is done on the gas (−W).
The equation $W = p Δ V$ assumes that the .......... does not change as the gas expands.
The equation $W = p Δ V$ assumes that the surrounding pressure does not change as the gas expands.
True or False?
The area under a p-V diagram only gives the work done when the pressure is constant.
False.
The area under a p-V diagram gives the work done even when both the pressure and volume change during the process, not only when pressure is constant.
What term is given to p-V diagrams in the context of engines?
Indicator diagrams.
Define an isobaric process.
An isobaric (constant pressure) process is one in which no change in pressure occurs. The work done is $W = p Δ V$ .
Define an adiabatic process.
An adiabatic process is one in which no heat is transferred into or out of the system, so $Q = 0$ .
What is true of the work done in an isovolumetric (constant volume) process, and why?
$W = 0$ , because there is no change in volume, so no work is done on or by the gas.
What is true of the internal energy in an isothermal process, and why?
$Δ U = 0$ , because the temperature does not change and internal energy depends on temperature.
In an adiabatic process, all the work done is at the expense of the system's .........., so the process is usually accompanied by a change in ...........
In an adiabatic process, all the work done is at the expense of the system's internal energy, so the process is usually accompanied by a change in temperature.
State the equation relating pressure and volume for an adiabatic process in an ideal gas.
$p V^{γ} = c o n s t a n t$
where γ is the ratio of specific heats, for example $γ = \frac{5}{3}$ for a monatomic ideal gas.
True or False?
In an isovolumetric process, $Q = W$ .
False.
In an isovolumetric process $W = 0$ , so from the first law of thermodynamics $Q = Δ U$ , not $Q = W$ .
Define the four-stroke petrol engine cycle.
An internal combustion engine cycle that burns fuel once every four strokes of the piston (induction, compression, power, exhaust), requiring two revolutions of the crankshaft. It is also known as the Otto cycle.
Describe what happens during the induction stroke of a petrol engine.
The piston moves down the cylinder, increasing the volume. A petrol-air mixture is drawn in through the inlet valve, at a pressure just below atmospheric pressure.
Describe what happens during the compression stroke of a petrol engine.
The inlet valve closes and the piston moves up, doing work on the gas adiabatically. Near the end of the stroke, the petrol-air mixture is ignited by a spark, causing pressure and temperature to rise rapidly at almost constant volume.
On the theoretical indicator diagram for a petrol engine, what happens between points B and C?
Heat is supplied and the volume is kept constant; this is when ignition by the spark occurs.
On the actual indicator diagram, the corners of the graph are .......... because the valves take a finite time to ...........
On the actual indicator diagram, the corners of the graph are rounded because the valves take a finite time to open and close.
Give two reasons why the area enclosed by the actual indicator diagram is smaller than the theoretical diagram.
- The expansion and compression are not perfectly adiabatic, so heat transfer occurs
- The heating and cooling cannot occur at truly constant volume
- Some exhaust gas or unburnt fuel vapour may be present, not pure air
True or False?
A four-stroke petrol engine cycle requires only one revolution of the crankshaft to complete.
False.
A full four-stroke cycle requires two revolutions of the crankshaft.
What is drawn into the cylinder during the induction stroke of a diesel engine, and how does this differ from a petrol engine?
Only air is drawn in, compared to a petrol-air mixture in a petrol engine, so there is no fuel present in the cylinder during compression.
How is the diesel fuel ignited in a diesel engine?
During compression, the air reaches a high enough temperature and pressure to vapourise and ignite the diesel fuel, which is injected directly into the cylinder as a fine spray through an injector (no spark plug is used).
On the theoretical indicator diagram for a diesel engine, what happens between points B and C?
Heat is supplied while the pressure is kept constant, unlike the petrol engine cycle, where heating occurs at constant volume.
The biggest difference between the actual and theoretical diesel indicator diagrams is that from B to C, there is no .......... at the start of the expansion stroke.
The biggest difference between the actual and theoretical diesel indicator diagrams is that from B to C, there is no sharp peak at the start of the expansion stroke.
True or False?
The compression stroke (A to B) in the diesel engine cycle occurs at constant pressure.
False.
The compression stroke is adiabatic, not constant pressure; both the pressure and temperature of the air increase from A to B.
What happens between points D and A on the diesel engine indicator diagram?
The system is cooled at constant volume.
Define compression ratio.
The compression ratio is the ratio of the volume enclosed at the beginning of the compression stroke to the volume enclosed at the end of the compression stroke, $\frac{V_{1}}{V_{2}}$ . Efficiency is directly proportional to the compression ratio.
Why do diesel engines require a higher compression ratio than petrol engines?
To raise the pressure and temperature of the air high enough for the diesel fuel to self-ignite without a spark.
What is pre-ignition, and what can cause it in a petrol engine?
Pre-ignition is when the petrol-air mixture self-ignites before the spark. It can be caused by a compression ratio that is too high, or by a build-up of carbon in the cylinder.
State two disadvantages of a diesel engine compared to a petrol engine.
- Diesel engines operate at higher working pressures, making them more expensive to produce as they must be more robust and stable
- They have a lower power-to-weight ratio
A diesel engine typically has a compression ratio of around .........., while a petrol engine has a compression ratio of around ...........
A diesel engine typically has a compression ratio of around 16, while a petrol engine has a compression ratio of around 10.
True or False?
Diesel engines produce more carbon monoxide, hydrocarbons and carbon dioxide than petrol engines.
False.
Petrol engines produce more of these pollutants than diesel engines. A catalytic converter can reduce these emissions, though not below diesel engine levels.
Define calorific value.
The calorific value of a fuel is the amount of energy the fuel stores per unit volume (or per unit mass).
Define indicated power.
The indicated power is the power developed in the cylinder of an engine: $I n d i c a t e d p o w e r = (a r e a o f p - V l o o p) \times (c y c l e s p e r s e c o n d) \times (n u m b e r o f c y l i n d e r s)$
State the equation for the input power of an engine.
$I n p u t p o w e r = c a l o r i f i c v a l u e \times f u e l f l o w r a t e$
How is friction power related to indicated power and brake power?
$F r i c t i o n p o w e r = i n d i c a t e d p o w e r - b r a k e p o w e r$
Part of the indicated power is used to overcome frictional forces within the engine, so the brake power is lower than the indicated power.
For a four-stroke engine, how many revolutions of the crankshaft make up one cycle?
Two revolutions.
The brake power of an engine is also known as the .......... power, and is equal to $P = T ω$ .
The brake power of an engine is also known as the output power, and is equal to $P = T ω$ .
True or False?
The brake power of an engine is always greater than its indicated power.
False.
The brake power is lower than the indicated power, because some of the indicated power is lost overcoming friction within the engine.
Define overall efficiency of an engine.
Overall efficiency is the ratio of brake power to input power. It is also the product of the thermal efficiency and the mechanical efficiency.
Define thermal efficiency of an engine.
Thermal efficiency is the ratio of indicated power to input power. It shows how well the engine transforms the chemical energy in the fuel into useful power in the engine cylinders.
Define mechanical efficiency of an engine.
Mechanical efficiency is the ratio of brake power to indicated power. It depends on the amount of energy lost to friction in the moving parts of the engine.
How is the overall efficiency of an engine related to its thermal and mechanical efficiencies?
Overall efficiency = thermal efficiency × mechanical efficiency.
Mechanical efficiency depends on the amount of energy lost due to .......... of the engine, caused by friction.
Mechanical efficiency depends on the amount of energy lost due to moving parts of the engine, caused by friction.
True or False?
Thermal efficiency is calculated as brake power divided by input power.
False.
That ratio is the overall efficiency. Thermal efficiency is the ratio of indicated power to input power.
Define the source in a heat engine.
The source is a high-temperature reservoir at temperature T_H, which supplies heat energy Q_H to the engine.
Define the sink in a heat engine.
The sink is a low-temperature reservoir at temperature T_C, which receives heat energy Q_C from the engine.
State the second law of thermodynamics in terms of extracting energy from a heat reservoir.
When extracting energy from a heat reservoir, it is impossible to convert it all into work. Equivalently, thermal energy cannot spontaneously transfer from a region of lower temperature to a region of higher temperature.
Why is it impossible for a heat engine to operate on the First Law of Thermodynamics alone?
If the engine reached the temperature of the source, no heat would flow because they would have reached thermal equilibrium, so no work would be done.
Heat engines convert thermal energy into .......... work, whereas heat pumps transfer heat energy from a low to a high temperature.
Heat engines convert thermal energy into mechanical work, whereas heat pumps transfer heat energy from a low to a high temperature.
True or False?
A heat engine that obeyed only the First Law of Thermodynamics, with no friction, would be 100% efficient.
True.
Such an engine would be 100% efficient in principle, but it cannot be built in reality because real engines always have frictional losses and so must also obey the Second Law.
Define the efficiency of a heat engine.
$e f f i c i e n c y = \frac{W}{Q_{H}} = \frac{Q_{H} - Q_{C}}{Q_{H}}$
Where W is the useful work output, Q_H is the energy transferred from the source and Q_C is the energy transferred to the sink.
Why can the efficiency of a heat engine never be 100%?
Because no heat engine can completely convert heat into work — some heat energy is always lost to the surroundings.
Define maximum theoretical efficiency.
$M a x i m u m t h e o r e t i c a l e f f i c i e n c y = \frac{T_{H} - T_{C}}{T_{H}}$
This applies when the engine's working substance is an ideal gas.
How should the source and sink temperatures be chosen to make an engine as efficient as possible?
The source temperature should be as high as possible and the sink temperature should be as low as possible.
The maximum theoretical efficiency of a heat engine is 100% only if the sink temperature is at ...........
The maximum theoretical efficiency of a heat engine is 100% only if the sink temperature is at 0 K.
True or False?
The maximum theoretical efficiency equation only applies to engines using a specific p-V cycle.
False.
This equation is valid for all idealised reversible engines, irrespective of the particular cycle or working substance.
A heat engine transfers 100 kJ from the source and rejects 25 kJ to the sink. Calculate its efficiency.
$e f f i c i e n c y = \frac{100 - 25}{100} = 0.75 = 75 %$
Give three reasons why practical heat engines have a much lower efficiency than their theoretical equivalent.
Any three from:
- Friction between moving parts, and heat lost through the cylinder walls
- Incomplete combustion of the fuel, so the temperature rise is lower than expected
- Power used to drive internal components such as pumps and motors
- The working gas is not an ideal gas
- The engine cycle processes are irreversible
Define imperfect combustion as a limitation of a real heat engine.
Heat energy is taken in and rejected over a range of temperatures, rather than entirely at the single temperatures T_H and T_C, so the maximum temperature is not always reached.
Why do the irreversible processes in a real engine cycle reduce its efficiency?
Energy is dissipated out of the system and there is no equilibrium with the surroundings, as the processes happen too quickly (for example, the valves take a finite time to open and close, and the strokes are not truly adiabatic).
Define a Combined Heat and Power (CHP) scheme.
A power station that uses the waste heat normally lost through cooling towers or a local river or sea to heat nearby homes and businesses, instead of removing it through cooling.
Why are CHP schemes not more widely used in the UK?
Most power plants are positioned far away from homes and businesses, so the waste heat has cooled down too much by the time it reaches them.
Conventional power stations are, in reality, about .......... efficient, compared with a maximum theoretical efficiency of around 61%.
Conventional power stations are, in reality, about 35% efficient, compared with a maximum theoretical efficiency of around 61%.
True or False?
A CHP scheme increases the useful work output, W, of the engine.
False.
A CHP scheme makes use of the wasted heat energy Q_C that would otherwise be lost through cooling — it does not increase W.
Define a reversed heat engine.
An engine that transfers heat energy from a cold space to a hot space by inputting work, such as a refrigerator or a heat pump.
Why must work be input to a reversed heat engine?
Heat energy naturally flows from a warmer to a colder space, so work must be done to force it to flow the other way.
What does a refrigerator aim to do, in terms of Q_C and W?
It aims to extract as much energy as possible from the cold space per joule of work done.
What does a heat pump aim to do, in terms of Q_H and W?
It aims to deliver as much energy as possible to the hot space per joule of work done.
In a heat pump used to heat a house, the outside is the .......... space and the inside is the hot space.
In a heat pump used to heat a house, the outside is the cold space and the inside is the hot space.
True or False?
A refrigerator and a heat pump work on different principles.
False.
They are identical in principle — both are reversed heat engines, and one could fulfil the function of the other, though less effectively.
Define the coefficient of performance (COP).
A measure of how effective a reversed heat engine is at transferring heat per unit of work done. It is not a measure of efficiency, as it can be greater than 1.
State the equation for the coefficient of performance of a refrigerator, COP_ref.
$C O P_{r e f} = \frac{Q_{C}}{W} = \frac{Q_{C}}{Q_{H} - Q_{C}} = \frac{T_{C}}{T_{H} - T_{C}}$
State the equation for the coefficient of performance of a heat pump, COP_hp.
$C O P_{h p} = \frac{Q_{H}}{W} = \frac{Q_{H}}{Q_{H} - Q_{C}} = \frac{T_{H}}{T_{H} - T_{C}}$
How is COP_hp related to COP_ref?
$C O P_{h p} = C O P_{r e f} + 1$
The coefficient of performance is a .........., so it has no units.
The coefficient of performance is a ratio, so it has no units.
True or False?
COP_hp is always greater than COP_ref.
True.
This is because Q_H is always greater than Q_C.
An ideal heat engine has an efficiency of 0.25 and runs in reverse, as a refrigerator, between the same hot and cold spaces. Determine COP_ref.
$Q_{H} = \frac{W}{0.25} = 4 W$
$Q_{C} = Q_{H} - W = 3 W$
$C O P_{r e f} = \frac{Q_{C}}{W} = \frac{3 W}{W} = 3$

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Rotational DynamicsNext:The Discovery of the Electron