Relate voltage, current and resistance
The idea
For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
Step by step
- For the stated ohmic model, voltage equals current multiplied by resistance: V = IR.
- Rearrange for the unknown quantity; current I = V ÷ R.
- Use the model’s conditions rather than assuming every device has constant resistance.
Example
An ideal ohmic resistor has resistance 4 Ω and voltage 12 V across it. What current flows?
Answer
3 A
I = V ÷ R = 12 ÷ 4 = 3 A.
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Use invented values to compare current at 6 V through 2 Ω and 3 Ω resistors. Work only on paper.
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