# Category: A Level Physics Chapters

## Black hole to ‘eat biggest meal’

Black hole to ‘eat biggest meal’ https://www.bbc.co.uk/news/world-middle-east-25678737

## What is the second law of thermodynamics?

What is the second law of thermodynamics?

https://www.gu.com/p/3kt6q  from The Observer

Thermodynamics is the study of heat and energy. At its heart are laws that describe how energy moves around within a system, whether an atom, a hurricane or a black hole. The first law describes how energy cannot be created or destroyed, merely transformed from one kind to another. The second law, however, is probably better known and even more profound because it describes the limits of what the universe can do. This law is about inefficiency, degeneration and decay. It tells us all we do is inherently wasteful and that there are irreversible processes in the universe. It gives us an arrow for time and tells us that our universe has a inescapably bleak, desolate fate.

Despite these somewhat deflating ideas, the ideas of thermodynamics were formulated in a time of great technological optimism – the Industrial Revolution. In the mid-19th century, physicists and engineers were building steam engines to mechanise work and transport and were trying to work out how to make them more powerful and efficient.

Many scientists and engineers – including Rudolf Clausius, James Joule and Lord Kelvin – contributed to the development of thermodynamics, but the father of the discipline was the French physicist Sadi Carnot. In 1824 he published Reflections on the Motive Power of Fire, which laid down the basic principles, gleaned from observations of how energy moved around engines and how wasted heat and useful work were related.

The second law can be expressed in several ways, the simplest being that heat will naturally flow from a hotter to a colder body. At its heart is a property of thermodynamic systems called entropy – in the equations above it is represented by “S” – in loose terms, a measure of the amount of disorder within a system. This can be represented in many ways, for example in the arrangement of the molecules – water molecules in an ice cube are more ordered than the same molecules after they have been heated into a gas. Whereas the water molecules were in a well-defined lattice in the ice cube, they float unpredictably in the gas. The entropy of the ice cube is, therefore, lower than that of the gas. Similarly, the entropy of a plate is higher when it is in pieces on the floor compared with when it is in one piece in the sink.

A more formal definition for entropy as heat moves around a system is given in the first of the equations. The infinitesimal change in entropy of a system (dS) is calculated by measuring how much heat has entered a closed system (δQ) divided by the common temperature (T) at the point where the heat transfer took place.

The second equation is a way to express the second law of thermodynamics in terms of entropy. The formula says that the entropy of an isolated natural system will always tend to stay the same or increase – in other words, the energy in the universe is gradually moving towards disorder. Our original statement of the second law emerges from this equation: heat cannot spontaneously flow from a cold object (low entropy) to a hot object (high entropy) in a closed system because it would violate the equation. (Refrigerators seemingly break this rule since they can freeze things to much lower temperatures than the air around them. But they don’t violate the second law because they are not isolated systems, requiring a continual input of electrical energy to pump heat out of their interior. The fridge heats up the room around it and, if unplugged, would naturally return to thermal equilibrium with the room.)

This formula also imposes a direction on to time; whereas every other physical law we know of would work the same whether time was going forwards or backwards, this is not true for the second law of thermodynamics. However long you leave it, a boiling pan of water is unlikely to ever become a block of ice. A smashed plate could never reassemble itself, as this would reduce the entropy of the system in defiance of the second law of thermodynamics. Some processes, Carnot observed, are irreversible.

Carnot examined steam engines, which work by burning fuel to heat up a cylinder containing steam, which expands and pushes on a piston to then do something useful. The portion of the fuel’s energy that is extracted and made to do something useful is called work, while the remainder is the wasted (and disordered) energy we call heat. Carnot showed that you could predict the theoretical maximum efficiency of a steam engine by measuring the difference in temperatures of the steam inside the cylinder and that of the air around it, known in thermodynamic terms as the hot and cold reservoirs of a system respectively.

Heat engines work because heat naturally flows from hot to cold places. If there was no cold reservoir towards which it could move there would be no heat flow and the engine would not work. Because the cold reservoir is always above absolute zero, no heat engine can be 100% efficient.

The best-designed engines, therefore, heat up steam (or other gas) to the highest possible temperature then release the exhaust at the lowest possible temperature. The most modern steam engines can get to around 60% efficiency and diesel engines in cars can get to around 50% efficient. Petrol-based internal combustion engines are much more wasteful of their fuel’s energy.

The inefficiencies are built into any system using energy and can be described thermodynamically. This wasted energy means that the overall disorder of the universe – its entropy – will increase over time but at some point reach a maximum. At this moment in some unimaginably distant future, the energy in the universe will be evenly distributed and so, for all macroscopic purposes, will be useless. Cosmologists call this the “heat death” of the universe, an inevitable consequence of the unstoppable march of entropy.

## UK China nuclear deal ‘Orwellian’

UK China nuclear deal ‘Orwellian’ https://www.bbc.co.uk/news/uk-politics-25156551

# Security fears over ‘Orwellian’ Chinese nuclear deal

By Rob BroombyBritish Affairs Correspondent, BBC World Service

It was hailed by UK Chancellor George Osborne as a “new dawn” – but serious questions remain about the security implications of Britain’s nuclear energy deal with China.

The UK government has refused to say whether China’s planned investment in the British nuclear industry was approved by the National Security Council – the body that assess the risks from foreign investment in critical national infrastructure projects.

Chancellor George Osborne announced during his trip to China in October that Chinese state owned companies CGN and CNNC would be allowed to take a 40% stake in the company planning to build the Hinkley C nuclear power station in Somerset.

In the future Chinese firms could become “majority owners of a British nuclear power plant subject to British safety rules and policed by the British,” said Mr Osborne.

Tim Yeo, chairman of Parliament’s energy and climate change committee, said Britain should “warmly welcome investment from China in the nuclear industry” but said he did not know whether the National Security Council had formally discussed or approved the investment.

“It would be a great pity if on some security reason this was thrown back into jeopardy.” he told BBC Radio 4’s The World Tonight.

But other members of Mr Yeo’s committee are worried.

Conservative MP Dr Phillip Lee said it was “perverse” and “Orwellian” to allow Chinese state owned firms a role in critical infrastructure projects like nuclear power at a time when questions over Chinese cyber-attacks on the west had not been resolved.

He said future conflicts would not be about the “physical possession of nations” but would involve “control of information, control of infrastructure, water electricity and communication.”

The Chinese could not take away a nuclear power station in the event of tension between the two countries but they could “virtually switch it off” if they wanted to, he claimed.

It would also bind Britain’s hands in respect of China diplomatically, when it comes to speaking out on human rights.

On the website of the China National Nuclear Corporation – one of the companies connected to the Hinkley project – the company boasts openly of its military links.

“China National Nuclear Corporation (CNNC) is the large state-owned enterprise under the direct management of the central government. Historically, CNNC successfully developed the atomic bomb, hydrogen bomb and nuclear submarines and built the first nuclear plant in the main land of China. CNNC is the main body of the national nuclear technology industry, the core of the national strategic nuclear deterrence”.

The company website says it “shoulders the dual historical responsibility for building the national defence force, increasing the value of state assets and developing the society.”

Hinkley Point C is set to take 10 years to become fully operational. It will be made up of two nuclear reactors and will be built next to Hinkley Point A and B.

Just days after George Osborne made his nuclear announcement Chinese state-run TV was showing-off its nuclear armed submarines for the first time in 42 years accompanied by rousing music.

Official Chinese news agency Xinhua called the subs an “assassin’s mace that would make adversaries tremble”.

Labour MP Dr Alan Whitehead, also a member of the energy and climate change committee called the Chinese nuclear company CNNC an “arm of the state”.

“There doesn’t appear to be a clear distinction between the role of the Chinese National Nuclear Corporation in developing civil nuclear and developing and forwarding military nuclear,” he told the World Tonight.

“Big corporations particularly national corporations in China are not companies in the way that we would see them in the UK.”

He said the Chinese military – the People’s Liberation Army – would be involved in some of the decisions made by the firm.

He has called on the UK government to state publicly how the investment in critical national infrastructure was approved and by whom.

Corruption case

Nuclear expert Mark Hibbs, of the Carnegie Endowment for International Peace, said the decision to invest in the British nuclear project would have been a “strategic decision” that would have been approved by China’s State Council – the nation’s ruling executive.

The UK Cabinet Office said in a statement that “the process for dealing with such issues falls under the aegis of the National Security Council”.

It said the government had “put in place an approach which enables it to assess the risks associated with foreign investment and develop strategies to manage them.

The National Security Council “brings together the economic and security arms of the government and is the forum that ultimately balances the risks and opportunities of inward investment decisions,” added the Cabinet Office statement.

But despite repeated requests the Cabinet Office has refused to say whether Chinese investment in Hinkley or the possible full majority ownership of nuclear reactors in the future has been formally discussed, assessed or approved by the National Security Council.

Critics fear Britain may be sleepwalking into nuclear relationship with China it will regret especially if in years to come China wants to introduce its own nuclear technology to the UK.

“The Chinese domestic nuclear programme certainly leaves much to be desired” says Dr Paul Dorfman of the University College London Energy Institute.

‘Safe power’

He is worried by the lack of transparency in the Chinese nuclear industry and cites the arrest and dismissal by the Chinese Government in August 2009 of the President of CNNC in a £260m corruption case involving allegations of “bid-rigging in nuclear power construction”.

Chinese investment in key energy infrastructure is “deeply problematic,” he said and industry experts were worried about “China’s weak regulatory structures”.

The UK Cabinet Office says Chinese firms have a “track-record in delivering safe nuclear power over the past thirty years. And that in the long-term it will deliver lower and more stable energy prices.”

“Any company involved in the UK nuclear power industry does so in accordance with the most stringent regulations in the world. On this basis, we welcome companies which can demonstrate the capability to contribute to safe nuclear power generation in the UK.”

The economics of the Hinkley C project have also been slammed. Peter Atherton of the respected city firm Liberum Capital said they were “flabbergasted” by the deal.

At £8bn per reactor, Hinkley Point is “the most expensive power station in the world (excluding hydro schemes) on a per megawatt basis,” said Mr Atherton.

He said the French and Chinese state owned firms would earn between £65bn and £80bn in dividends from British consumers over the project’s lifetime.

“The UK government was taking a massive bet that fossil fuel prices will be extremely high in the future. If that bet proves wrong then this contract will look economically insane when HPC (Hinkley Point C) commissions” added Mr Atherton.

Tim Yeo said the budget was so high “because they have factored in a much bigger contingency in to this project”.

But he added: “I do believe it is in Britain’s interests to have part of its electricity generated by nuclear power.

“It is a secure, safe, clean, low- carbon source of electricity.”

# Beer brewing could help make better bricks

THERE’S more to brewing than beer. A by-product of the process could be about to give an upgrade to a workhorse building material – red clay bricks. By blending in the grains left over from making beer, the bricks can be more environmentally friendly and better insulators.

Bricks are often impregnated with polystyrene as a way to enhance their heat-trapping abilities. This is appealing, because the bricks remain strong, and they can be built into energy-efficient buildings, says Eduardo Ferraz of the Polytechnic Institute of Tomar in Portugal. However, EU restrictions on carbon emissions have made it expensive to incorporate polystyrene and other synthetic materials into bricks.

Ferraz and his colleagues have now shown that brewery grains can be mixed into clay bricks to enhance their ability to trap heat, without compromising strength.

Spent grain for the process should be easily available, because commercial breweries produce huge quantities of it as a pulpy mixture that is usually used in animal feed or ends up in landfill.

With a clay paste containing 5 per cent spent grains, the team was able to create bricks just as strong as the conventional type, while reducing the amount of heat they lost by 28 per cent (Journal of Materials in Civil Engineering, doi.org/p6k). The reason for this, the team says, is that the grains make the bricks more porous, and so they trap more air, which increases heat retention.

One thing could stand in the way of using this process, though: the smell. Bill Daidone of the Acme Brick Company, one of the largest brick manufacturers in the US, says his lab abandoned experiments because the stench of the moist grains was overpowering. “We opened up the bucket and it was terrible,” he says. This problem vanishes once the bricks are fired, though, says Ferraz.

Bricks that provide insulation without sacrificing strength could be a big boost to the brick industry, says John Sanders, a researcher at the National Brick Research Center at Clemson University in South Carolina.

“With the current concern for energy codes, I think the industry is open to change,” Sanders says.

## IceCube detector finds first solid evidence for cosmic neutrinos

IceCube detector finds first solid evidence for cosmic neutrinos

https://www.gu.com/p/3ktbm

Thu 21 November 2013
Scientists have found the first solid evidence for cosmic neutrinos, ghostly particles created in violent events in the far reaches of the universe.
Neutrinos are subatomic particles that hardly ever interact with the atoms that make up stars, planets and us. Detecting them is tough: in the latest study, researchers detected 28 at the IceCube detector, built under the ice of the south pole.
“This is a huge result. It could mark the beginning of neutrino astronomy,” said Darren Grant, assistant professor of physics at the University of Alberta and one of the leaders of the IceCube Collaboration, which involves more than 250 physicists and engineers from a dozen countries.
Neutrinos are electrically uncharged particles that have a tiny mass, formed in the nuclei of atoms. Travelling at near the speed of light, they hardly interact with anything and could easily fly through a light year of lead. But there are unimaginable numbers of them in the universe: trillions of them from the sun pass through each of us every day.
Scientists know that neutrinos with even higher energy than those already observed should come from cosmic explosions, such as gamma ray bursts, black holes and active galactic nuclei, far away in the universe. Detecting these high-energy neutrinos would give scientists a way to peer inside some of the most violent processes going on at the farthest reaches of the cosmos.
Until now, scientists have used other detectors to see low-energy neutrinos created in cosmic-ray collisions in the Earth’s upper atmosphere and particles from a nearby supernova known as 1987A. The 28 neutrinos detected at IceCube are much higher energy and come from as yet unidentified sources far out in the cosmos. The results were published in the journal Science on Thursday.
“I’ll bet that 20 years from now we’ll look back and say, yeah, this was the start of neutrino astronomy,” John Learned, of the University of Hawaii, Manoa, told Science magazine.
To find the particles, scientists built a detector into a cubic kilometre of ice in Antarctica. After melting holes in the ice, they lowered 86 strings of light detectors, around 5,000 in total, to depths between 1.5km and 2.5km. Neutrinos can interact with atomic nuclei, and when that happens in the ice around a detector the collisions create an avalanche of charged light-emitting particles. That light can be measured by the detectors and, the brighter the light, the more energetic the original neutrino was.
IceCube has been on the hunt for neutrinos since 2010. Since then scientists have found evidence for 28 neutrinos with energies higher than 30 teraelectronvolts (TeV). Two of the particles had energies greater than 1,000 TeV. In comparison, the biggest particle accelerator ever made, the Large Hadron Collider at Cern, will collide particles at 14TeV when its upgrade is completed in 2015.
Since they do not interact with anything, the cosmic neutrinos found at IceCube are useful to scientists because they point in straight lines to where they came from. The few they detected are not enough to pinpoint any location in particular but, according to the project scientist Gregory Sullivan, of the University of Maryland, the IceCube team will look for further detections in coming years, “like waiting for a long exposure photograph”, to fill in their emerging picture of the faraway cosmos.

## Microwave signals turned into power

Microwave signals turned into power https://www.bbc.co.uk/news/technology-24897584