Can a Coronal Mass Ejection (CME) cause a blackout on Earth and why? Can a Coronal Mass Ejection (CME) cause a blackout on Earth and why is it so what's the relation between electro magnetic radiations and electrical and electronic appliance.what exactly does it do to the appliance
 A: Space weather events, such as CMEs, can cause rapid variations (seconds to 10s of minutes) in the Earth's geomagnetic field which can induce an electric field on the surface of the Earth. This electric field induces electrical currents in the power grid and other (grounded) conductors. A consequence of this could be transformer burn out or other network instabilities. The appliance itself is unlikely to be effected, but its power supply could be.
From Delores Knipp's "Understanding Space Weather and the Physics Behind it":

The chain of events for GICs begins with a time-varying magnetic field external to Earth that induces electric currents in the conducting material on and under the surface. These currents are usually strongest in the auroral electrojets, but tropical regions could feel a similar short-lived effect caused by an anomalous electrojet created by severe compressions of Earth's dayside magnetic field.
As a consequence of Faraday's Law of Induction, an electric field at the Earth's surface is induced buy the time variations of the magnetic field. The surface electric field causes the GICs to flow into any conducting material.

These Solar events are unlikely to cause a transformer to fail (although it is not impossibe). Instead we usually see that transformers in the high latitudes have significantly shorter lifetimes. This is likely due to repeated exposure of low level GICs, rather than the one off "super" events. Indeed, (again from Knipp's book):

Statistically, the failure rate [of transformers] follows the solar cycle, but with a three year lag.

The classic example is that of the Hydro-Quebec grid from 1989 (see [Bolduc, 2002][1]).
GIC effects can also be seen in pipelines which intensify existing corrosion problems at certain points. And also in railways, due to the long, continuous, nature of the network. One example, from July 1982, was that a GIC-associated change in the voltage caused safety systems to assume a train was short-circuiting the rails. Also it caused traffic signals to change colour. The amount of current that is induced in the network can vary between 10s and 100s of amps [Bolduc, 2002; Lloyds, 2010][1,2], but the exact amount depends on a variety of factors including severity of storm, geological conditions and latitude.
There are, however, many more potential impacts of a CME impact on Earth though than just a potential blackout, these include: radiation impacts on satellites, ionising radiation on aircraft passengers/crew, impacts on GNSS and other radio communication systems.
CMEs increase the fluxes of radiation particles at the Earth. For satellites, electrons cause electrostatic charging and false aging. This is particularly problematic for satellites at geostationary orbit. Satellites in low Earth orbit (LEO) are more protected, but can still be affected especially at high latitudes. These effects can also penetrates further down into the Earth's atmosphere, and effect airline passengers/crew. It is expected that a person on board a commercial jet, flying at "normal" altitudes, would experience the same radiation effects during a solar storm as undergoing a chest CT scan. This "only" raises the lifetime cancer risk by 1 in 1,000 but is still a consequence that is worth considering. It is also one of the reasons why women up to the 12th week of pregnancy, are advised not to fly. The radiation effects would be much more harmful for such a young fetus.
Finally, space weather events (such as CMEs and solar flares) have a major effect on the Earth's ionosphere. The increased solar radiation ionizes the atmosphere, creating more free electrons. These free electrons interact with radio signals and can refract or even reflect them. Systems which work between 10 MHz and 2 GHz, are going to experience faults or total loss of communication. For GNSS, the ionosphere is taken into account on a day-to-day basis. However during solar storm events the refraction of the signal by the ionosphere can cause an error in position of 10s - 100 metres. These events do not just instantly dissipate either. It could take several days for the ionosphere to return to "normal" conditions and GNSS work again as expected.
There have been a number of studies which have looked into the consequences of severe space weather events (solar "superstorms") on Earth's infrastructure. One was published in the UK last year by the Royal Academy of Engineering, which is available online, in full, here. Which I recommend if you would like a more detailed description of Space Weather and its potential impacts.
Edit (1): I have provided some more physics information as requested by Brandon.
Edit (2): Updated details about amount of induced current.
[1]: Bolduc, L. (2002), GIC observations and studies in the Hydro-Québec
power system, J. Atmos. Sol. Terr. Phys., 64, 1793-1802.
[2]: Lloyds (2010), Space Weather; Its impact on Earth and implications for business. http://www.lloyds.com/~/media/lloyds/reports/360/360%20space%20weather/7311_lloyds_360_space%20weather_03.pdf
A: We (colleagues of mine and I at NASA) did a study recently to look into the impacts of a Carrington-like event.  Fortunately, the way our power grids work leaves a great deal of somewhat unintended protections in the system.  The story about the $3 trillion (USD) storm that you may be referring to assumed that these (unintended?) safe guards (i.e., if one transformer blows out, all the rest in a grid tend to trip rather than blow out too) failed and we lost 150 transfer station transformers (i.e., the ones the size of small houses that take months to build and cost millions of US dollars).
The cause for concern relates to ground induced currents (GICs).  It's a similar principle that causes an electrical arc to form when you unplug a toaster that is on.  Due to the dipole geometry of Earth's magnetic field and the direction from which a CME impact would occur, the places that experience the strongest effects are at high latitudes (i.e., near the poles).  Thus, as one might expect, countries like Norway are investing a lot of money into research on this topic because they have had issues with GICs in their power grids and pipelines (basically any long conductor is susceptible and the effect is proportional to the length of the conductor).
Conversely, in this same study we found that our satellites would not be so fortunate.  Anything at or outside of geosynchronous orbit on the dayside (i.e., side facing the sun) of Earth could suffer irrecoverable radiation and electrical damage.  This could potentially cause a tremendous amount of damage, financial and physical, to our satellite infrastructure.  The impact would be felt by anyone with a cell phone, TV, internet, or those that rely upon GPS (e.g., most militaries and commercial airlines).
So the most recent idea is that our satellites are very vulnerable but our power grids may not be as vulnerable as we originally thought (though, all of these issues are incredibly difficult to model and predict so take my comments with a grain of salt).
A: The impact on the Earth's magnetosphere causes it to fluctuate and that induces high currents in things like power lines. These are potentially so great they can cause surge arresters to trip and close down parts of the electricity grid. A Carrington Event would be so great that it could melt grid power transformers and cause massive damage that might take months to fix.
A: Yes. See "The Quebec Blackout", Nasa News, March 13, 2009

On Friday March 10, 1989 astronomers witnessed a powerful explosion on the sun. Within minutes, tangled magnetic forces on the sun had released a billion-ton cloud of gas. It was like the energy of thousands of nuclear bombs exploding at the same time. The storm cloud rushed out from the sun, straight towards Earth, at a million miles an hour. The solar flare that accompanied the outburst immediately caused short-wave radio interference, including the jamming of radio signals from Radio Free Europe into Russia. It was thought that the signals had been jammed by the Kremlin, but it was only the sun acting up!
On the evening of Monday, March 12 the vast cloud of solar plasma (a gas of electrically charged particles) finally struck Earth's magnetic field. The violence of this 'geomagnetic storm' caused spectacular 'northern lights' that could be seen as far south as Florida and Cuba. The magnetic disturbance was incredibly intense. It actually created electrical currents in the ground beneath much of North America. Just after 2:44 a.m. on March 13, the currents found a weakness in the electrical power grid of Quebec. In less than 2 minutes, the entire Quebec power grid lost power. During the 12-hour blackout that followed, ...

A: Note that the way a transformer would fail is not directly due to the induced current. Rather what happens is that these induced currents magnetize the core of the transformer (the currents are, of course not constant DC currents but the frequency is so extremely low that over a period of many minutes they can be considered to be effectively DC currents). This then makes the the power transmission through the transformer a bit less efficient, more of the energy of the powerplant is now going to be dissipated as heat, and that can be enough to cause the transformer to explode because of the extremely high power that is transmitted through the transformer.
