Practical takeaway
Ohm’s law connects three bench quantities: voltage, current and resistance. If you know any two, you can calculate the third.
Electricity & Electronics
Ohm's Law
Use one relationship to connect voltage, current and resistance.
TECHNICIAN FOUNDATION3 of 16
Technician exam focus
Be able to use E = I × R, I = E ÷ R and R = E ÷ I. When the answer uses division, E is the numerator.
The memory pattern
EIR
Use whichever memory method works for you. The triangle is optional. The equations are E = I × R, I = E ÷ R, and R = E ÷ I. A handy pattern: whenever the answer uses division, E is on top.
E = I × R
Voltage equals current times resistance.
I = E ÷ R
Current equals voltage divided by resistance.
R = E ÷ I
Resistance equals voltage divided by current.
STEMulation
Pick what you want to solve
The same three quantities in the equation are shown on the circuit: source voltage, resistor value, and current through the loop.