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What causes the water molecule to have an electric dipole moment?
What causes the water molecule to have an electric dipole moment?
What are induced dipoles primarily caused by?
What are induced dipoles primarily caused by?
What is the relationship between the distance from a dipole and the electric field strength, according to the content?
What is the relationship between the distance from a dipole and the electric field strength, according to the content?
In the electrogram procedure described, what is the purpose of the galvanometer?
In the electrogram procedure described, what is the purpose of the galvanometer?
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Which of the following statements about electric charges in the described experiment is correct?
Which of the following statements about electric charges in the described experiment is correct?
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What does Δφ represent in the electrogram method?
What does Δφ represent in the electrogram method?
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To achieve zero current detected by the galvanometer, what condition must be met?
To achieve zero current detected by the galvanometer, what condition must be met?
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What is the primary purpose of creating an equipotential line in the experiment?
What is the primary purpose of creating an equipotential line in the experiment?
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What does resistivity measure?
What does resistivity measure?
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Which ions are typically responsible for good conductivity in living tissues?
Which ions are typically responsible for good conductivity in living tissues?
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In which scenario is a Wheatstone's bridge typically used?
In which scenario is a Wheatstone's bridge typically used?
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Which of the following factors does not affect the resistivity of an electrolyte?
Which of the following factors does not affect the resistivity of an electrolyte?
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What is the formula for calculating resistance when resistivity, distance, and cross-sectional area are known?
What is the formula for calculating resistance when resistivity, distance, and cross-sectional area are known?
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What happens in a Wheatstone's bridge when points C and D are equipotential?
What happens in a Wheatstone's bridge when points C and D are equipotential?
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Which type of substances are referred to as electrolytes?
Which type of substances are referred to as electrolytes?
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How does temperature affect the resistivity of an electrolyte?
How does temperature affect the resistivity of an electrolyte?
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What is the primary reason for the high electric resistance in living organisms?
What is the primary reason for the high electric resistance in living organisms?
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What type of tissues are classified as having low conductance?
What type of tissues are classified as having low conductance?
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What does the term impedance (Z) refer to in the context of living tissues?
What does the term impedance (Z) refer to in the context of living tissues?
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Which equation represents the modified Ohm's law for living tissues?
Which equation represents the modified Ohm's law for living tissues?
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What is the purpose of taking multiple l1 and l2 readings before calculating R'?
What is the purpose of taking multiple l1 and l2 readings before calculating R'?
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What effect does passing direct current (d.c.) through living tissue have over time?
What effect does passing direct current (d.c.) through living tissue have over time?
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How is the electrolyte resistance R'' calculated during the experiment?
How is the electrolyte resistance R'' calculated during the experiment?
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What physiological measurement does rheography provide to doctors?
What physiological measurement does rheography provide to doctors?
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Which formula is used to calculate electrolyte resistivity?
Which formula is used to calculate electrolyte resistivity?
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At what frequency range is the subthreshold of a.c. commonly applied in rheography?
At what frequency range is the subthreshold of a.c. commonly applied in rheography?
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What does the variable ΔE represent in the thermoresistor theory?
What does the variable ΔE represent in the thermoresistor theory?
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What is the unit of capacitance mentioned for living tissues?
What is the unit of capacitance mentioned for living tissues?
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Why is it important to check the resistance R for the same temperature values during heating and cooling?
Why is it important to check the resistance R for the same temperature values during heating and cooling?
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In the context of the thermoresistor, what does the term 'tg β' represent?
In the context of the thermoresistor, what does the term 'tg β' represent?
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What is the significance of calculating the value of S in the procedure?
What is the significance of calculating the value of S in the procedure?
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How do you determine the activation energy ΔE using the slope of the lnR vs. 1/T graph?
How do you determine the activation energy ΔE using the slope of the lnR vs. 1/T graph?
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What is the relationship between resistor R and tissue impedance Z when the circuit is adjusted?
What is the relationship between resistor R and tissue impedance Z when the circuit is adjusted?
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At what frequency is the output frequency set during the measurement process?
At what frequency is the output frequency set during the measurement process?
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Which formula is used to measure tissue impedance in relation to frequency f?
Which formula is used to measure tissue impedance in relation to frequency f?
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What does the rheostat slider position indicate at the moment when the effect is first felt?
What does the rheostat slider position indicate at the moment when the effect is first felt?
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What type of oscilloscope is most commonly used for biomedical purposes?
What type of oscilloscope is most commonly used for biomedical purposes?
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What must be noted after the voltage is increased until a current effect is felt?
What must be noted after the voltage is increased until a current effect is felt?
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Which of the following is NOT a use of an oscilloscope in biomedical applications?
Which of the following is NOT a use of an oscilloscope in biomedical applications?
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What is calculated after taking impedance measurements at different frequencies?
What is calculated after taking impedance measurements at different frequencies?
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Study Notes
Electric Dipole Moment
- Electrons in a water molecule spend more time near the oxygen atom, giving the molecule an electric dipole moment.
- Random fluctuations in molecular configurations can cause temporary charge separation, leading to a dipole moment.
- This dipole moment creates an electric field, which induces dipoles in nearby molecules.
- The potential of the dipole electric field at a distance r is Φ = k - p - cosθ/(εr²).
- At large distances (r >> 1), the electric field strength is E = k - p - cosθ/(ε - r¹).
- Dipoles are useful in biomedical models of electric fields generated by single cells and electrograms.
Measuring Electric Field Lines
- Goal: To visually represent electric field lines.
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Materials:
- Plate with wet sand
- Galvanometer
- DC source
- Two point-like electrodes
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Method:
- Connect a DC source to the electrodes, creating an electric field.
- Use a galvanometer to identify equipotential points, which are points with the same electrical potential.
- Connect equipotential points with lines to form equipotential lines.
- Electric field lines are perpendicular to equipotential lines, pointing from the positive to the negative pole.
- Calculate the electrical field strength using the formula E = -ΔΦ/Δs, where ΔΦ is the potential difference measured by the galvanometer and Δs is the distance between the points.
Measuring Electrolyte Resistivity
- Goal: To measure the resistivity of an electrolyte.
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Theory:
- Electrolytes are substances that conduct electricity in solution or in the fused state due to the presence of ions.
- Electrolytic dissociation refers to the separation of substances into ions (anions and cations) when dissolved.
- Resistivity (ρ) is the resistance of a substance with unit length and cross-section.
- Electrolyte resistivity depends on concentration, temperature, and the type of electrolyte.
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Materials:
- U-shaped glass tube
- Electrodes
- Wheatstone's bridge
- AC source
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Method:
- Connect the circuit as shown in Fig. 2.
- Calculate the electrolyte resistance (R) using the Wheatstone's bridge, using the formula R = R₁(l₂/l₁), where R, is the known resistance, and l₁, l₂ are lengths of the wire.
- Calculate resistivity (ρ) using the formula ρ = (R × S)/L, where S is the cross-section area and L is the distance between the electrodes.
Measuring Thermoresistor Resistance
- Goal: To study the relationship between the resistance of a thermoresistor and temperature.
-
Theory:
- The resistance of a semiconductor at temperature T is R = R₀·exp(ΔE/(k·T)), where R₀ is the resistance at high temperatures, ΔE is the activation energy, and k is Boltzmann's constant.
- The relationship between lnR and 1/T is linear with a slope of ΔE/(2·k), allowing for the calculation of ΔE.
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Materials:
- Thermoresistor
- Voltmeter
- Ammeter
- Rheostat
- Heating source
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Method:
- Connect the circuit as shown in Fig. 2.
- Measure the thermoresistor resistance (R) at room temperature.
- Increase the thermoresistor temperature and measure R at different temperatures.
- Plot lnR = f(1/T) and calculate the slope of the line.
- Calculate ΔE using the formula ΔE = 2·k·tgβ, where β is the slope of the line.
Measuring Tissue Impedance
- Goal: To measure the impedance of living tissue.
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Theory:
- Living tissue opposes the flow of electric current due to capacitance and ohmic resistance.
- The impedance (Z) is the total opposition to current.
- Tissue impedance depends on blood supply and is used in diagnostic rheography.
- DC current decreases in living tissue due to polarisation, making AC current a more suitable option.
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Materials:
- AC generator
- Voltmeter
- Rheostat
- Electrodes
- Cloth moistened in NaCl solution
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Method:
- Connect the circuit as shown in Fig. 3.
- Measure the tissue impedance (Z) at different frequencies (f).
- Calculate the resistance (R) and capacitance (C) using the formulas:
- C = (RZ₁Z₂)/(2πZ₁Z₂f₁f₂)²
- R = √(Z₁² - (2πf₁C)²)/1 - (f₁/f₂)²
- Draw conclusions based on the measured values.
Oscilloscope
- The oscilloscope is a device that displays a visual image of rapidly varying electrical quantities.
- It is used to measure the duration, amplitude, and form of feeble electric oscillations.
- In biomedical applications, it is used to display electrograms (EEG, ECG, ERG, EMG) and biopotentials of single cells.
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Description
Explore the concepts of electric dipole moments and how they interact with electric fields. This quiz covers the properties of dipoles, their measurement, and their applications in biomedical models. Test your understanding of the calculations and experimental procedures involved in visualizing electric field lines.
