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### Course: MCAT>Unit 9

Lesson 11: Current and resistance

# Electrolytic conductivity

Liquids can also conduct electricity. Explore the concept of electrolytic resistivity and conductivity in liquids. Learn how to measure these properties using a known voltage, an ammeter, and two plates submerged in a solution. Discover how impurities can affect the current flow and the resistivity of the solution. Created by David SantoPietro.

## Want to join the conversation?

• Why would we use AC current to measure the resistivity of water? How does using AC prevent electrolysis?
• The electrodes alter their polarity 50 or 60 times a second. The heavy ions can not follow such high frequencies. So they can’t be discharged effectively. As a result the electrolysis is almost unnoticeable. But if water is the solvent, at each terminal small bubbles are noticed due to high mobility of H+ and OH-. They can migrate to the electrodes owing to their high mobility. Hence a mixture of H_2 and O_2 is formed at each electrode.

Credits: Parantap Nandi, Department—Electrical Engineering, West Bengal University of Technology (WBUT).
• Why was Edison so opposed to alternating current? I heard he killed an elephant with it and invented the electric chair just to try prove how dangerous it was.
• he opposed it because someone could use it to oppose his own inventions!
(1 vote)
• at , we suppose that the electrons go straight from one plate to the other, right?
• The ions you mean. Positive and negative ions are the charge carriers here, not electrons. And no, here the system works differently, the positive ions move to the negative electrode and the negative ions move to the positive electrode. There they get discharged by gaining/losing electrons from/to the electrode. This is how electrolytes conduct electricity.
• What is the difference between a Volt and a current? A current is obviously a flow of electrons but what is a volt and and why are there two meters like Ammeter and Voltmeter?
• Voltage is what makes the current. Voltage is analogous to water pressure for flowing water. Higher the pressure, the more the flow. Specifically voltage is the potential energy per unit charge, and the positive charges will want to flow from regions of high voltage to low voltage. Similar to how a ball will roll down a hill from a region of high gravitational potential energy to a region of low gravitational potential energy.
• Why would L/A have to remain the same, what if we brought the the plates closer. And why is it not the area of cross section the liquid?
• By maintaining constant L/A in your apparatus you can measure resistivity of different easily. Resistivity would be the only variable and everything else in the experiment is constant, so you can measure the resistance and figure out resistivity quickly!

Hope that helps.
• Can anyone tell me more about AC current. And the difference between AC and DC current.
• in DC the current goes 'directly' from positive to negative.
In AC, the direction 'Alternates' going back and forth. Like the electrons are vibrating in time with one another.

make sense?
• AC is alternating current but what is DC
(1 vote)
• DC stands for "direct current". It is the unidirectional flow of electric charge.
(1 vote)
• How to find resistivity of fluid?