Electrical Conductivity Lab Report

Electrical Conductivity Lab Report Martin Yamane BCCC Physics 107 Abstract/Introduction: In this lab experiment, we explored the concept of electrical currents, resistance in terms of Ohm’s Law, and conductivity. The aim of the experiment was to determine the conductivity of tap water before and after adding sodium chloride. Our results show that conductivity increases with each addition of salt. Theory: The ability of electrons to flow from atom to atom in consecutive lines down a material is the material’s conductivity. Conductors are materials that allow easy passage of electrons. Most metals are considered conductors because the electrons surrounding their atoms act as a single sea allowing electrons to flow freely. Insulators are materials that are relatively resistant to allowing an electric current through. Most non-metals are insulators. Resistance and conductivity are inverse measurements. Resistance is voltage over current. Adding salt to tap water will increase its conductivity by polarizing the liquid allowing electrons to move from ion to ion. Results: Resistor – 316 ohms Salt (grams)

Voltage (V)

0 1 2.6

3.99 4.40 6.56

Current (V/R) (mA) 12.6 13.9 20.8

Voltage Drop 8.01 7.60 5.44

Conductivity Water (mS) 1.6 1.8 3.8

Voltage drop of water found by subtracting total voltage (12 V) from voltage drop of resistor. This uses Kirchoff’s voltage law to determine the voltage drop of the water. Conductivity of water is found by finding the total resistance of the circuit by dividing total voltage (12 V) by total current, subtracting the resistance of the resistor, then finding the reciprocal. Ex (((12V/12.6mA)X10^3)-316)X10^-1=1.6mS

Graphs:

Conductivity 4 3.5 3 2.5 2

Conductivity

1.5 1 0.5 0 0

1

2

3

Resistance vs Salt Mass 0.7 0.6 0.5 0.4 Resistance

0.3 0.2 0.1 0 0

0.5

1

1.5

2

2.5

3

These graphs show that there is an exponential relationship between the mass of salt and the resistance/conductivity of the water. With each addition of salt, the water’s ability to conduct an electrical current increased. Discussion: The addition of sodium chloride increases conductivity because the salt dissociates into Na+ and Cl- ions that allow the passage of electrons. The Na+ ions will congregate towards the negative electrode while the Cl- ions move towards the positive electrode. The electrons are transferred from negative electrode to positive ion and electrons are transferred from negative ion to positive electrode. Electrons are transferred from the neutral Na atoms to the neutral Cl atoms between the

electrodes and this process repeats indefinitely allowing the solution to act as a conductor. Performing this experiment was beneficial to our understanding of the conductivity of different materials to electricity along with our understanding of Kirchoff’s Laws.