Visualization of the result
Observation No. 1
In a circuit of constant resistance :
As the voltage increases, the current increases proportionally.
When the voltage is decreased, the current decreases proportionally.
The U/I ratio gives a result equal to the value of the resistance inserted in the circuit.
Experience #1
Complete the circuit by inserting a 12 Ω resistor.
Vary the voltage from 2 to 6V across the 12 Ω resistor.
For each voltage value, note the intensity of the corresponding currents on the ammeter.
Complete the table and calculate the U/I ratio.
In this case, if we plot the potential difference as a function of current, we obtain the following image.
Also, on this graph, the slope of the line is the value of the resistance.
When we have this relationship between ∆V and I for a material, we say that it is an " ohmic material ".
Experiment #2
Apply a constant voltage of 6V across a 12 Ω, 24 Ω and 48 Ω resistor.
Note the corresponding current value for each resistor.
Complete the table and calculate the product RI
Visualization of the result
"The current intensity (I)" being proportional to "the voltage (U)" across the resistor and inversely proportional to "the resistance (R)", we can derive the following mathematical relationship.
Observation No. 2
In a constant voltage circuit:
As the resistance increases, the current decreases proportionally.
As the resistance decreases, the current increases proportionally.
The product R . I gives a result equal to the value of the voltage.
