Beginner
Ohm's Law & DC Circuits
The simple relationship between voltage, current and resistance.
STEP 1 · CONCEPT
Voltage pushes current through a resistance. Double the voltage, double the current.
STEP 2 · SERIES
Same current flows through each element; resistances add up.
STEP 3 · PARALLEL
Same voltage across each branch; reciprocals of resistances add up.
WORKED EXAMPLE
A 12 V battery across a 4 Ω resistor: I = 12/4 = 3 A, power = 12 × 3 = 36 W.
Formulas
Ohm's law
V = I R
V volts, I amps, R ohms
Power
P = V I = I²R = V²/R
P watts
Parallel
1/R = 1/R₁ + 1/R₂
Practice questions
Q1.Two 10 Ω resistors in parallel give…
Ohm's Law & DC Circuits · Easy
Q2.A 60 W bulb on 240 V draws about…
Ohm's Law & DC Circuits · Medium
Q3.Power dissipated in 2 Ω carrying 3 A?
Ohm's Law & DC Circuits · Medium