ch 5 - Electrostatics and Magnetism

Question 1

electrical potential of dipole

Answer 1

V=(kq)/rsub1 - (kq)/rsub2 = (kq(rsub2 - rsub1))/rsub1rsub2
At greater distance: V = ((kqd)/rsquared) x costheta;

d = distance between +q and -q (source charges); rsub1 = distance between the chosen point in space and +q; rsub2 = distance between said point and -q

Question 2

dipole moment (p)

Answer 2

SI units are C x m: p = qd

Question 3

perpendicular bisector of the dipole

Answer 3

plane that lies halfway between +q and -q. Because the angle between this plane and the dipole axis is 90 degrees (and cos 90 = 0) the electrical potential at any point along this plane is 0.

Question 4

electric dipole

Answer 4

result of two equal and opposite charges being separated a small distance (d) from each other; can be transient or permanent

Question 5

magnitude of the electric field on the perpendicular bisector of the dipole

Answer 5

E = 1/(4pi x epsilonsub0) x p/r^3

Question 6

electrostatic constant (k)

Answer 6

8.99 x 10^9 (N x m^2)/C^2

Question 7

net torque on dipole

Answer 7

T = pE sintheta where p = magnitude of dipole moment (p = qd), E = magnitude of uniform external electric field, and theta = angle the dipole moment makes with the electric field; this will cause dipole to reorient itself so that its dipole moment (p) aligns with the electric field E

Question 8

equipotential lines

Answer 8

lines on which the potential at every point is the same; potential difference bt any two points on an equipotential line is zero

Question 9

SI unit for magnetic field strength

Answer 9

tesla (T) 1 T = 1 (N x s)/(m x C); or when smaller measured in gauss. 10^4 gauss = 1 T

Question 10

diamagnetic materials

Answer 10

made of atoms with no unpaired electrons and that have no net magnetic field; can be called weakly antimagnetic

Question 11

Paramagnetic materials

Answer 11

have unpaired electrons; weakly magnetized in the presence of an external magnetic field, aligning the magnetic dipoles of the material with the external field (ex aluminum, copper and gold)

Question 12

Ferromagnetic materials

Answer 12

have unpaired electrons and permanent atomic magnetic dipoles that are normally oriented randomly so that the material has no net magnetic dipole. will become strongly magnetized when exposed to a magnetic field or under certain temps (iron, nickel and cobalt)

Question 13

for infinitely long and straight current-carrying wire, equation for magnitude of magnetic field

Answer 13

B = (fancy u sub 0 x I)/(2pi r) I (i) = current in the wire; r = perpendicular distance of the current from the wire; B = magnetic field; fancy u sub 0 = permeability of free space (4pi x 10^-7 (T x m)/A)

Question 14

right hand rule for straight wire magnetic fields

Answer 14

point thumb in direction of current and wrap fingers around current-carrying wire. Fingers mimic circular field lines curling around wire

Question 15

magnitude of magnetic field at center of circular loop of current carrying wire

Answer 15

B = (fancy u sub 0 x I)/2r r = radius of loop; fancy u sub 0 = permeability of free space (4pi x 10^-7 (T x m)/A); B = magnetic field; I = current in wire

Question 16

Lorentz force

Answer 16

sum of the electrostatic and magnetic forces acting on charges in magnetic field

Question 17

magnetic force

Answer 17

F sub B = qvB sin theta; q = the charge; v = magnitude of velocity, B = magnitude of magnetic field; theta = smallest angle between the velocity vector v and the magnetic field vector B; unit is N

Question 18

right-hand rule of magnetic forces

Answer 18

to determine direction of the magnetic force on moving charge; position right thumb in direction of the velocity vector; put fingers in direction of magnetic field lines; palm points in the direction of the force vector for a positive charge, while back points in direction of force vector a negative charge

Question 19

For a straight wire, magnitude of force created by external magnetic field

Answer 19

F sub B = ILB sin theta; I (i)= current; L = length of wire in the field; B = magnitude of magnetic field; theta = angle between L and B

Question 20

fancy uC = how many coulomb?

Answer 20

1 x 10^-6 C