Measuring Resistivity

Question 1

What is an electrolyte?

Answer 1

A substance that conducts electricity in solution or in the fused state due to the presence of ions.

Question 2

What is electrolytic dissociation?

Answer 2

The reversible separation of certain substances in oppositely charged ions, anions and cations, as a result of the solution.

Question 3

State an example of electrolytic dissociation?

Answer 3

H2SO4 –> 2H+ + SO4-2

Question 4

What is the symbol for resistance?

Answer 4

looks like a lowercase “p”

Question 5

What is resistivity measured in?

Answer 5

Ohm meters

Question 6

What is mass resistivity?

Answer 6

The product of resistivity and density.
resistivity x density

Question 7

What does the resistivity of an electrolyte depend on?

Answer 7

• electrolyte concentration
• electrolyte temperature
• type of electrolyte

Question 8

Tissues containing much liquid are what? —-conductors with —-resistivity

Answer 8

good conductors with low resistivity

Question 9

What are some good conducting tissues?

Answer 9

blood, lymph, spinal liquid

Question 10

What are some poor conducting tissues?

Answer 10

bone, dry skin

Question 11

What are some medium conducting tissues?

Answer 11

muscle

Question 12

How can one measure tissue resistivity?

Answer 12

Using a U-shaped glass tube filled with electrolytes and electrodes inserted in it.

Question 13

What is the equation used to measure tissue resistivity?

Answer 13

R = p*L/S

R= resistance
p= electrode resistivity
L= distance between the electrodes
S= cross section area of the glass tube

Question 14

What type of current is applied to the electrodes to avoid their polarization?

Answer 14

A.C. source

Question 15

When is the A.C. source balance position reached?

Answer 15

when buzzing diminished or dissapears

Question 16

What is the procedure to measuring tissue resistivity?

Answer 16

1) connect the circuit
2) place the electrode in a U-shaped tube at definite height MN.
3) Switch on the A.C. source, select R value of such magnitude that the balance point D were close to midpoint of AB.
4) Take I1 and I2 readings.
5) Repeat positions 4-3 times and retake the mean values of I1 and I2. Calculate R’x.
6) Move the electrodes upwards and in the same way calculate resistance R’‘x.
7) Calculate R’‘x and R’x difference.
8) Take the readings NN and MM and sum up. The sum on NN + MM is length L in m.
9) Take diameter D of the internal tube, and calculate S.
10) Calculate the electrolyte resistivity.
11) Fill in a table with the data obtained.