Delwell SC CV
53. Mutual induction can be used as the basis for a metal
detector. A typical set-up uses two large coils that are
parallel to each other and have a common axis. Because
of mutual induction, the ac generator connected to the
primary coil causes an emf of 0.46 V to be induced in
the secondary coil. When someone, without metal objects,
walks through the coils, the mutual inductance and, thus,
the induced emf do not change much. But when a person
carrying a hand gun walks through, the mutual inductance
increases. The change in emf can be used to trigger an
alarm. If the mutual inductance increases by a factor of
three, find the new value of the induced emf.​

-first use of geothermal energy occurred more than 10,000 years ago in north america by american paleo-indians

-the first industrial use of geothermal energy began near pisa, italy in late 18th century

-in 1904, italian scientist piero ginori conti invented the first geothermal electric power plant in which steam was used to generate the power

-with the above experiment, the first geothermal plant in usa started in 1922 with a capacity of 250 kilowatts

-however, in 1946 first ground-source geothermal heat pump installed at commonwealth building in portland, oregon

-during the 1960’s, pacific gas and electric began operation of first large scale geothermal power plant in san francisco, producing 11 megawatts

-in 1973, when oil crisis began many countries began looking for renewable energy sources and by 1980’s geothermal heat pumps (ghp) started gaining popularity in order to reduce heating and cooling costs

-as effect of climate change started showing results, governments of various countries joined hands to fight against it, for which kyoto protocol was signed in japan in 1997, laid out emission targets for rich countries and required that they transfer funds and technology to developing countries, 184 countries have ratified it

hope this

i don't understand. explain it clearly

cant without the picture! ?