Dipole

Question 1

What is an electric field defined by?

Answer 1

1) electric field strength
2) electric potential

Question 2

What is the symbol for the “electric field strength”?

Answer 2

E with an arrow on top

Question 3

What is the equation for calculating the electric field strength?

Answer 3

E (arrow) = F (arrow) / q

E (arrow)- electric field strength
F (arrow)- net electric force
q- magnitude (of the test charge)

Question 4

What do fields do? What does that cause?

Answer 4

they superimpose each other, forming a single net field.

Question 5

What does the vector specify? What is a vector?

Answer 5

The vector specifies the magnitude of the net field at any point.
It is the vector sum of the values of fields due to each individual source.

Question 6

What is Coulombs law? What does it explain?

Answer 6

Coulomb’s law describes the strength of the electrostatic force (attraction or repulsion) between two charged objects.

Question 7

What is the Coulombs law equation?

Answer 7

E= k*q / Er^2

E- electric field
k- permitivity constant
q- charge
E-
r- radius

Question 8

What is the symbol for potential?

Answer 8

φ
o with a vertical line going across it.

Question 9

What is the electric potential?

Answer 9

The amount of work needed to move a unit charge from a low potential region to a high potential region against an electric field.

Question 10

What is the equation for electric potential?

Answer 10

φ=W/q

φ- electric potential
W- work
q- charge

Question 11

What does q stand for?

Answer 11

charge

Question 12

What does W stand for

Answer 12

work

Question 13

What is the equation for the potential φ of charge q?

Answer 13

φ = kq / (er)

φ- potential
k- constant
q- charge
e- emittance
r- radius

Question 14

How to express the electric field strength as a ratio in regards to potential difference?

Answer 14

E (arrow) = -dφ / dr
E (arrow) = - gradient φ

E (arrow) - electric field strength
φ - potential

Question 15

What does the minus sign represent in the ratio of the gradient of potential to the electric field strength?

Answer 15

the field strength direction coincides with a decrease in potential.

field strength and potential are inversely correlated.

NOTE: the greater the field strength (closer together), the smaller the electric potential (less work had to be done to carry the “ball” up).

Question 16

What does a dipole consist of?

Answer 16

• two charges
• equal magnitude
• opposite charge
• held at a fixed distance
• make up a single unit

Question 17

What is magnitude?

Answer 17

The absolute or relative direction or size in which an object moves in the sense of motion.

Question 18

What constitutes to the dipole moment?

Answer 18

the product of the charges or their seperation.

Question 19

What is the equation for the dipole moment?

Answer 19

p (arrow) = (q*1) (arrow)

p- vector quantity (pointing fro the negative charge to the positive charge)

Question 20

What are the units of the dipole moment?

Answer 20

C×m

Question 21

Why do some molecules have a dipole moment?

Answer 21

Because they exhibit a charge seperation.

Question 22

Why does water have an electric dipole moment?

Answer 22

Because the electrons in a water molecule spend most of their time in the proximity of oxygen.

Question 23

Why does a molecule develop a dipole moment?

Answer 23

Random fluctuations in the configuration of a molecule lead to charge separation causing a molecule to develop a dipole moment.

Question 24

What does a dipole moment give rise to? What is the further effect?

Answer 24

Dipole moments give rise to electric fields which cause charge separation in nearby molecules, giving them a dipole moment as well.

Question 25

What are induced dipoles?

Answer 25

The dipole molecules which were formed due to a surrounding molecule being a dipole (having random fluctuations in configuration) and generating an electric field.

Question 26

What is the equation used to calculate the potential of the dipole electric field?

Answer 26

φ = k * p * cos⊜ / (e*r^2)

φ- potential of the dipole
k- contant
p- vector quantity
⊜- angle between teh dipole axis and the line seperating the given point
e- emmitence
r- radius

Question 27

How is the dipole model useful?

Answer 27

It is useful in biomedical descriptions of electric fields, generated by single cells and electrograms.

Question 28

How can one measure the dipole effect?

Answer 28

Using a plate filled with wet sand, a galvanometer, a DC source, and two point-like electrodes.

Question 29

What is the source of the electric field in the wet-sand box procedure?

Answer 29

the DC source

Question 30

Which direction do electric field signs travel?

Answer 30

from the positive pole to the negative pole.

Question 31

What does the charge trace coincide with?

Answer 31

The charge trace coincides with the electric field lines (As electric charges flow along the lines of electric fields).

Question 32

How can the sand bath potential difference be detected?

Answer 32

using a galvanometer

Question 33

When is no current detected?

Answer 33

when there is zero magnitude.

Question 34

What is the equation for calculating the electric field strength between electrodes?

Answer 34

E = -∆φ / ∆s

E- electric field strength
φ- potential (estimated by the galvanometer)
s- separation of arms

Question 35

What is ∆φ in other words?

Answer 35

∆φ = I * R

∆φ- electric potential
I - current
R- resistivity (ohms)

Question 36

What is the principal method of investigating the dipole moment?

Answer 36

1) The sand in a plate is moistened (not too much), then the surface is smoothed and pressed.
2) connect the DC to the poles L1 and L2.
3) Divide the line between the poles into
eight equidistant intervals.
4) Put one arm of the galvanometer to
point 1, another - some distance apart in such a way such that the pointer would be at its initial (zero deflection) place (change in potential=0).
Draw a line connecting the points (all these points have the same potential).
5) Repeat the analogous operation for points 2,….,7.
6) Calculate the electric field strength between electrodes using the
formula:

E = -∆φ / ∆s