Investigation of Kirchoff's Second Law
Aim: To investigate if Kirchoff's 2nd law is true- "The total current
I is equal to the sum of the currents distributed across the branches
of the parallel circuit i.e. Total I = I1 + I2"
Background information: Kirchoff's Law states that the source current
is divided between the two resistors in parallel (according to the
ratio depending on the resistance offered by each resistor).
Ohm's law states that the current in a circuit is inversely
proportional to the circuit resistance. This fact is true in both
series and parallel circuits. There is a single path for current in a
series circuit. The amount of current is determined by the total
resistance of the circuit and the applied voltage. In a parallel
circuit the source current divides among the available paths.
In a parallel circuit (like the two examples above), each device is
directly connected to the power source. This means that each device
receives the same voltage. The amount of current flowing through each
device is dependent on the impedance/resistance of that particular
device. If devices are added to the power source in a parallel
configuration, the current demand/flow from the power source
increases.
Hypothesis: If the total current in the circuit is = z then the sum of
the current of the 2 branches of the circuit will also = z. Hence, the
current recorded will be equal to the sum of the current of the 2
branches.
Apparatus: 1 Pal-pack, 1 Multimeter, set of conducting wires, fixed
resistors of 80Ω and 20Ω.
Method: Follow the following steps:
* Turn the voltmeter knob till it reads 6 Volts; short the pal-pack
and turn the knob of the ammeter till it reads 1 Ampere.
* Connect the 2 resistors in parallel as shown below.
* Set the pal-pack to 6V and record the current.
* [IMAGE]Repeat the same thing only with 5V and then 4V and then 3V