1.1 use the following units: kilogram (kg), metre (m), metre/second (m/s),metre/second2 (m/s2), newton (N), second (s) and newton/kilogram (N/kg)
1.2P use the following units: newton metre (Nm), kilogram metre/second (kg m/s) (Triple)
A physical quantity is something that can be measured. For any measurement, the unit being used must be stated to give an understanding of the scale of the measurement.
For example, distance can be measured in kilometres or in miles. They are similar, but not the same and it is important to identify which was used for the measurement, to know how far the distance actually is.
Système Internationale d’Unités
The units that scientists use all over the world are standardised in the Système Internationale d’Unités – SI units. It is important to remember these six fundamental (or ‘base’) units of measurement:
There are many quantities scientists measure that come from the base units. These derived units are very useful to quote as measurements, but they are not fundamental as they come from fundamental units.
For example, frequency is the number of times something happens per unit of time.
This is a useful quantity, but it is a division into the time unit.
The standard unit for frequency is considering the number ‘per second‘, which is called ‘hertz, Hz’, but this comes from the fundamental unit ‘second‘.
If you want to do a lesson on iGCSE Electricity 2.2 understand how the use of insulation, double insulation, earthing, fuses and circuit breakers protects the device or user in a range of domestic appliances.
Here are some resources to help you. I have attached all the lesson slides and if you work through this, you can then do an iSpring Quiz.
This is a great “technical practical” that you can use to investigate how a lever works, but in a fun practical way. It requires some tricky kit, so you might need to go do to the local tyre shop to see if they will let you have a go!
Force Sensor (range 0.1N to 500N) (link – for suggested type of sensor)
“Diesel has emerged as the dominant fuel type for company cars, as a result of great fuel efficiency, performance and low cost of ownership under the government’s CO2 emissions based tax regime,” says Gerry Keaney, chief executive of the British Vehicle Rentals and Leasing Association, whose members own or fleet manage more than three million cars in the UK.
“But the diesel proportion of new registrations has been falling gradually for some time, as modern petrol powered cars have become better at delivering similar benefits, and we expect this trend to gather pace.”
In the UK, even company car buyers now see downsized petrol engines, many emitting around 100g/km CO2, as a viable, efficient alternative to diesel.
This is not just down to “anti-diesel sentiment”, says Al Bedwell, director, global powertrains at LMC Automotive. “It has more to do with petrol getting better and staging a fight-back, especially in small cars in Western Europe.”
Manufacturers such as Ford, Opel/Vauxhall, Hyundai and Volkswagen are all offering similarly downsized petrol engines these days, many emitting around 100g/km of CO2.
In Europe, diesel’s share of the market is set to drop from 53.3% of the market in 2014 to 51.5% in 2015, says Mr Bedwell, then continue sliding to 35% by 2020.
Turbo chargers are traditionally associated with diesel engines, which needed a boost to give them more oomph. They weren’t “much fun to drive” without them, says Guillaume Devauchelle, head of innovation and science at automotive technology company, Valeo.
And the relative cost of adding turbo to an expensive diesel engine was lower, he explains.
But turbos are now increasingly infiltrating petrol engines because they deliver dramatic emissions reductions and improvements in fuel economy, without sacrificing performance, says Craig Balis, chief technology officer of Honeywell Transportation Systems, the world’s largest turbo maker.
A two-litre turbo-charged four cylinder petrol engine can match the output of a three-litre naturally aspirated V6 petrol engine, he says, so “the technology we have is really a no-compromise solution”.
Turbos work by using the engine’s exhaust gas to drive a turbine, which in turn drives a compressor, which compresses air. This air is then forced into the combustion chamber where it mixes with fuel to create additional power.
This means the engine won’t have to burn so much fuel to deliver the same output.
“Our turbos for passenger vehicles have turbines that spin at 200,000-300,000 revolutions per minute (rpm), generating temperatures of up to 1,000 degrees Celsius, so the metal is literally glowing red,” Mr Balis says.
By comparison petrol engines operate at just 6,000-7,000 rpm and diesel at 5,000-6,000rpm.
To cope with such extreme speed, pressure and heat, turbos need to be incredibly robust, so Honeywell is using ball bearings and other technologies that have been developed for military aircraft by the company’s aerospace division.
The turbos are also coupled with intercoolers that cool the airflow and increases its density as it is supplied to the engine, and with oil cooling systems that prevent overheating.
Turbos are often combined with direct or indirect fuel injectors and variable valve lift or timing systems to make the process even more efficient.
Electrified superchargers, which compress air for just a few hundred milliseconds to add brief low-end torque until the turbo charger kicks in, will also hit the market in the next few months.
Over the next five years, we’ll go from about a third to around half the cars sold having turbo chargers, and the growth will continue. We call this the ‘golden age of turbo’
Terrence Hahn, Honeywell TS
E-chargers, or e-turbos, will transform the driving experience, believes Mr Devauchelle, as they eliminate what’s called turbo lag – that slight delay in power boost you experience after pressing the accelerator.
“The turbo increases the engine’s maximum power. The e-charger gets you there even quicker,” he explains.
As such, e-turbos may rival established twin-turbo technology, where a small turbo takes care of the early stages of acceleration before the second turbo takes over.
The e-turbos’ batteries can be recharged in different ways, for instance by capturing energy during braking, explains Mr Hahn.
With enough electric power, e-chargers could take over more and more of the work done by the turbo.
Eventually carmakers will redesign vehicle architecture, moving from standard 12-volt batteries to higher voltage systems.
Forty-eight volt architecture is emerging in luxury cars with many electric components, but e-chargers can also run on 12-volt batteries if they are only required to deliver brief boosts, explains Mr Devauchelle.
‘Golden age of turbo’
“Petrol power is moving from naturally aspirated engines to turbo charged engines at a faster rate than ever before,” says Terrence Hahn, president and chief executive of Honeywell Transportation Systems.
“Over the next five years, we’ll go from about a third to around half the cars sold having turbo chargers, and the growth will continue,” he predicts.
“We call this ‘the golden age of turbo’.”
But there is no silver bullet as carmakers continue to grapple with ever-stricter emissions regulation, coupled with huge penalties for non-compliance.
Any number of combinations of e-chargers, turbo chargers, multi-stage boosting, fuel injection, variable valve systems, and combustion-electric hybrid technologies are being explored.
“During 30 years in the industry, I have never before seen so much diversity,” says Mr Devauchelle.
In a cramped laboratory on the campus of the University of California San Diego (UCSD), graduate student Lizzie Caldwell is hard at work, painting tiny squares of metal with a fine mist of black paint.
As experiments go, it doesn’t look terribly impressive.
Yet the paint she is using is highly sophisticated – the result of intensive research. It is also probably one of the blackest materials ever created.
What the research team at UCSD are trying to do is make large-scale solar power generation more viable, by creating a material which can absorb a greater quantity of sunlight than existing coatings, and last longer.
Heart of darkness
The paint is being developed for a new generation of so-called concentrating solar power plants (CSP).
These use thousands of mirrors to focus sunlight on a central tower, which is coated with a dark, light-absorbing material. The light is converted into intense heat, which is used to make steam. The steam can then be used to drive turbines, in order to produce electricity.
It is a very clean form of power generation, and existing plants which use coal or other fossil fuels can be converted to use the technology. In addition, heat can be stored so that power generation can continue even when the sun isn’t shining.
However, there’s a catch. The light-absorbing coatings which are currently used aren’t really up to the job.
They aren’t efficient enough, can’t withstand the highest temperatures and, out in the elements, bombarded with intense sunlight, they don’t last very long either.
According to Professor Renkun Chen, who is helping to lead the research, the new material will be very different.
“First of all, it can absorb the light at a very high efficiency. And secondly, it can withstand very high temperatures in air, above 700 degrees Celsius. That isn’t possible with existing materials”, he says.
The secret of the new paint lies in nanotechnology – creating a surface made up of layers of microscopic particles. It is designed to minimise reflection.
The research team claims that it can convert up to 90% of the sunlight it captures into heat.
“The size of these particles matches the wavelengths of light, which is in the order of a few nanometres”, Prof Chen says.
“So when light gets in, it will get trapped. It’s as though it gets lost in a miniature forest, and never comes out”.
That is the theory, at any rate. But the mosaic of small metal tiles lined up in the lab for testing is testament to how challenging it is to put that theory into practice.
Each one represents a slightly different technique or chemical formula, as the team searches for the right balance of light absorption and durability.
Fifty shades of black, if you like.
“Right now we’re just playing with a lot of different ideas that we’ve been talking about for the last few months and years” says Lizzie Caldwell.
“We want to make sure we get the perfect, blackest colour”.
Run for the sun
The research has been funded by the US government’s SunShot initiative, which hopes to make solar energy as financially competitive as other forms of power generation by the end of the decade.
It isn’t just happening in the United States. In China, generous subsidies have led to a very rapid growth of solar power generation over the past few years.
This has come partly in response to the country’s voracious appetite for power and the need to curb severe urban pollution. But China has also become a major exporter of cheap solar technology, which has brought prices down worldwide.
And according to Professor Chen, CSP in particular has the potential to become a major source of clean energy in developing countries, reducing their reliance on burning fossil fuels such as coal.
Renowned environmentalist Denis Hayes, who now leads the Seattle-based Bullitt Foundation, thinks that we could be heading for a golden age of solar power.
“With solar, if you take a unit of area, there’s only so much sun that is going to strike it,” he says.
“So if you can get twice as much electricity out of that sunshine, and it costs no more or even less than before then suddenly you’ve transformed the market”.
He thinks that one day, entire cities could be powered by the energy of the sun, with the fabric of the buildings themselves being used to trap solar energy.
It’s fair to say that such a sunny utopia remains a very long way off. However, research such as that being carried out at UCSD just might bring it a little bit closer.
So if there is a golden age approaching, it may owe a debt to some very, very black paint.