Electricity and Magnetism Answers

1. An alpha particle is sent directly toward a target nucleus containing 92 protons. The alpha 

particle has an initial kinetic energy of 0.48pJ. What is the least center to center distance 

the alpha particle will from the target nucleus (assuming the nucleus does not move)?

2. Three +0.12C charges from an equilateral triangle 1.7m on a side. Using energy supplied

At the rate of 0.83KW, how many days would be required to move one of the charges to 

the midpoint of the line joining the other two charges?

3. The electric potential difference between the ground and a cloud in a particular 

thunderstorm is 1.2X109 V. In the unit of electron- volt, what is the magnitude of the 

electric potential energy of an electron that moves between ground and the clouds?

4. Angelo was choosing springs to use their door. He noticed that spring A was stiffer than spring B; that is ka> ka. Which spring will have more elastic potential energy stored if (a) they are compressed the same distance and (b) if the same force is applied on them?

1. Shaniya and Maxine move a box of toy with a mass of 20 kg from an initial position to one that is 8 m away towards the right. Shaniya on the left of the box pushes the box with a force of 5 N at an angle of 10? downward from the horizontal while Maxine on the right of the box pulls it with a force of 5 N 200 abovethe horizontal. The forces exerted by both girls are constant. What is the net work (Wnet) the two girls exert on the box?

Someday a person will walk on Mars, which is 5.6 x 10¹⁰ m from the earth at the closest approach. Determine the minimum time that will be required for a message from Mars to reach the earth via radio waves.

Excess carriers are uniformly generated in a GaAs photoconductor at a rate of GL = 1021 cm-3-s-1. The area is A = 10-4 cm2 and the length is L = 100 μm. The other parameters are:

Nd=5×1016cm-3 Na=0

μn=8000cm2/V-s μp=250cm2/V-s

If a voltage of 5 volts is applied, calculate (a) the steady-state excess carrier concentration, (b) the photoconductivity, (c) the steady-state photocurrent, and (d) the photoconductor gain.

 A positive point charge Q is placed on the −x-axis at x = −a, and a negative point charge −Q is placed on the +x-axis at x = a. A positive point charge q is located at some point on the +y-axis. (a) In a free-body diagram, show the forces that act on the charge q. (b) Find the x- and y-components of the net force that the two charges Q and −Q exert on q. (Your answer should involve only k, q, Q, a and the coordinate y of the third charge.) (c) What is the net force on the charge q when it is at the origin (y = 0)? (d) Graph the x component of the net force on the charge q as a function of y for values of y between −4a 

Two point charges separated by a distance of 30cm in air. One of the charges is positive and has a magnitude of 10 micro coulombs and the other is a negative charge of magnitude 15 micro coulombs. Calculate the force between the charges, state if it is force of attraction or repulsion

The concentrated charges of 0.25microcoulombs each are located at the vertices of an equilateral triangle of 10cm side. Find the magnitude and direction of force on one charge due to other charges

PP1//1

Two identical conducting spheres, one that has an initial charge +Q, the other initially uncharged, are brought into contact. What is the new charge on each sphere?

(a) +Q

(b) +Q/2

(c) zero

(d) -Q/2 (e) -Q

What is the total charge on an infinite wire carring a charge density

λ =

1

|x|+α where α is a cosntant. Find electric potential at a point

whose perepndicular distance from the wire at x = 0 is R