Solve a problem

Electric circuitsPhysicsHigh schoolabout 0:57

A 100 W appliance runs on 230 V. What current does it draw and what is its resistance?: animated lesson

A narrated, step-by-step electric circuits video lesson with captions. Final answer: current I = 0.434783 A; R = 529 Ω.

SpeedLanguage

Video with a synthetic English voice and captions. Pick another language for subtitles in that language, or open the interactive version.

Video narrated by a synthetic voice (Piper TTS, en_US-ljspeech-high voice (LJ Speech dataset, public domain)); the steps come from our maths engine and the answer was checked independently. Download MP4 (0.4 MB) · Captions (WebVTT)

Steps on screen

1. The problem
Worked example
A 100 W appliance runs on 230 V. What current does it draw and what is its resistance?
2. Step by step
1. $P = VI$
  Formula: electric power
2. $I = \frac{P}{V}$
  Rearrange for current I
3. $I = \frac{(100)}{(230)} = 0.434783\ \text{A}$
  Substitute the known values
4. $R = \frac{V}{I} = 529\ \Omega$
  Resistance (Ohm's law)
3. The answer
$\text{current I = 0.434783 A; R = 529 Ω}$
current I = 0.434783 A
4. Check
- Substituted every value back into the formula: both sides agree ✓

Transcript

The problem. Here is the problem: A 100 W appliance runs on 230 V. What current does it draw and what is its resistance? Use the electric power formula, rearranged for the unknown, in SI units.

Step by step. Formula: electric power. Rearrange for current I. Substitute the known values. Resistance (Ohm prime s law).

The answer. So the answer is current I equals 0.434783 A; R equals 529 Ω. Electric power is the rate at which energy is transferred: P equals VI. Combined with Ohm prime s law it can also be written P equals I squaredR equals V squared/R. A 60 W bulb on 120 V draws 0.5 A.

Check. Substituted every value back into the formula: both sides agree, which checks out.

About electric circuits

Ohm's law, electrical power and resistors in series and parallel.

A 100 W appliance runs on 230 V. What current does it draw…