Physics Answers

Given the altitude and the zenith distance of a star as 50 degree 25minutes and 39 degree 35minutes respectfully calculate for the declination and latitude of the star

At one corner of a 3cm by 4cm rectangle is placed a charge of -20pc and at the two adjacent corner are charge of 10pc .calculate the potential at the fourth corner.

A normal hydrogen atom consist of a proton nucleus and oribital electron , each carrying a charge (e).assuming that the electron orbit is circular and the seperation between the particles is 5.3×10^-11m.find

(I) the force of electrical attraction between the particles

(II) the electron oribital speed

A conducting sphere of radius 4×10^-3 has a charge 6.66pc.find workdone in bringing a unit charge to the surface of the sphere from infinity

A box of mass 40kg is being dropped along the floor by a rope inclined 60degree to the horizontal.The frictional force between the box and the floor is 100N and the tension of the rope is 300N. How much work in dragging the box through a distance of 4m

A badminton shuttle is struck, giving it a horizontal velocity of 73

m/s [W]. Air resistance causes a constant acceleration of 18 m/s2

[E]. Determine its velocity after 1.6 s.

The angular velocity of a wheel rotating on a horizontal axle point west. In what direction is the linear velocity of a point on the top of the wheel? If the angular acceleration points east, describe the tangential linear acceleration of this point at the top of the wheel. Is the angular speed increasing or decreasing?

A brass rod is 2m long at a certain temperature. What is the length for a temperature rise of 100k.(take x=0.000018-1)

Problem - A sample of gallium arsenide (GaAs) is doped with 1010 silicon atoms per cm3

.

Ninety-five percent of the silicon atoms replace arsenic atoms and the remaining five percent

replace gallium atoms. T = 300 K. The intrinsic carrier concentration, ni

, is equal to 9 × 106 cm3

.

Calculate the electron and hole concentration as well as the position of the Fermi level.

Problem – A silicon wafer is doped with 2×1016 boron and 1016 phosphorus atoms per cm3

.

Calculate n, p, and EF at room temperature assuming complete ionization. Repeat the same for 8

x 1015 boron atoms per cm3

and 1016 phosphorus atoms per cm3

.