Kirchhoff’s Rules*


To determine the electric current through and the voltage across various resistors in DC circuits.

PhET App Used

DC Circuits Kit


Activity 1. Loop Rule

Build the following circuit and measure the voltage across each element.

For the loop abca, measure the voltage drop in Volts across each element. Does it add up to zero?

Vab Vbc Vca Vtot

Repeat for acda loop

Vac Vcd Vda Vtot

Activity 2. Junction Rule

Measure the electric current in Amps through each resistor on the circuit above. Does the current in equal to the current out?

I10 I30 I50 Iin Iout

Activity 3. Post-lab calculations

Given the resistances and the batteries are known, calculate the electric current through the resistors. Compare your theoretical results with the your results from Activity 2.

Write down two loop equations (for the loops from Activity 1) and one junction equation (for the currents from Activity 2). Solve the three equations for the three unknown electric currents.

Note. You do not need to solve the set of three equations with three unknowns by hand. You can use either your calculators or Wolfram Alpha.

Question. Do your calculations for the electric current through each resistor agree with the results from the simulation?