Ohm’s Law and Basic Circuit Relationships

Manual: General · Subject: Electronics

Learn the simplest quantitative rules used to calculate voltage, current, resistance, and power.

The most important beginner law

Ohm’s law describes the relationship between voltage, current, and resistance: $V = IR$ where $V$ is voltage, $I$ is current, and $R$ is resistance.

You can also write $I = \frac{V}{R}$ and $R = \frac{V}{I}$ .

Resistance measures how much a component opposes current. Higher resistance means less current for the same voltage.

A useful power formula is $P = VI$ . Using Ohm’s law, you can also write $P = I^2R$ and $P = \frac{V^2}{R}$ .

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Important caution

Formulas are only useful when the units are correct. Always check that voltage is in volts, current in amperes, and resistance in ohms.

If voltage stays the same and resistance increases, what happens to current?

It increases It decreases It stays the same It becomes infinite

What is the symbol for resistance?

Ohm’s law summary