1. You are designing a new solenoid and experimenting with material for each turn. The particular turn you are working with is a circular loop of radius 3.50 cm that carries a current of 15.0 A . Calculate the magnetic field B at the center of the loop.
2. Consider the coordinate system in the figure. If the circular loop lies in the xy plane and if the current flows clockwise around the loop, which direction does the magnetic field point inside the loop?
A. Positive x.
B. Positive z.
C. Negative y.
D. Negative z.
3. If we decrease the radius the magnetic field will:.
A. Increase.
B. Decrease.
C. Stay the same.
D. None of the above.

Explanation:

1 ) Magnetic field due to a circular coil carrying current

= μ₀I / 2r

I is current , r is radius of the wire , μ₀ = 4π x 10⁻⁷

= 4π x 10⁻⁷ x 15 / (2 x 3.5 x 10⁻²)

= 26.9 x 10⁻⁵ T

2 )

Negative z direction .

The direction of magnetic field due to a circular coil having current is known  

with the help of screw rule or right hand thumb rule.

3 )

If we decrease the radius the magnetic field will:__increase .

A. Increase.

Magnetic field due to a circular coil carrying current

B = μ₀I / 2 r

Here r is radius of the coil . If radius decreases magnetic field increases.

So magnetic field will increase.

the results is a decrease in air temperature with an increase of altitude.

explanation:

-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