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.

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2