Electricity 1 — DC Circuits

Ohm's law & power

ELI5: think of electricity as water in a pipe: voltage is the water pressure, current is the flow rate, resistance is how narrow the pipe is. I = V/R — push harder (more volts) and more flows; squeeze tighter (more ohms) and less flows. Power, how fast energy turns into heat or light, is P = V·I.

V_{s} := 12 V

= 12 V supply voltage

R_{1} := 60 ohm

= 60 ohm

I_{1} = \frac{V_{s}}{R_{1}}

= 0.2 A current through R₁

P_{1} = V_{s} \cdot I_{1}

= 2.4 W power dissipated

Real-world hook: Ohm's law sizes the resistor in every gadget, explains why a short circuit (R ≈ 0) draws a dangerous surge, and why thick extension cords (less resistance) run power tools safely.

Try it yourself: what current flows when 24 V is applied across an 8 Ω resistor? (I = V/R.)

I_{you} := 24 V / 8 ohm

= 3 A ✏️ Your turn: divide 24 V by 8 Ω. The answer carries units of amps.

✓ pass

abs(I_{you} - 24 V / 8 ohm) < 0.001 A

green when your current is correct