Section 4.2: Ohm’s Law

Ohm’s Law is a fundamental principle in electrical circuits that relates voltage (V), current (I), and resistance (R) in a conductor. It applies to many resistive elements in DC circuits.

  • Ohm’s Law: \[ V = I \cdot R \] where \(V\) is voltage in volts, \(I\) is current in amperes, and \(R\) is resistance in ohms.
  • Current: Flow of charge, directly proportional to voltage and inversely proportional to resistance.
  • Resistance: Opposition to current flow. Ohm’s Law assumes constant temperature.

Example: Finding Resistance

A current of 2 A flows through a resistor when a voltage of 10 V is applied. Find the resistance.

Using Ohm’s Law: \( R = \frac{V}{I} = \frac{10}{2} = 5 \, \Omega \)

Practice Problems

  1. A resistor has 12 V across it and 3 A of current. Calculate its resistance.
  2. If a 5 Ω resistor carries 2 A, determine the voltage across it.
  3. A 10 V battery is connected across a resistor of unknown value. If the current is 0.5 A, find the resistance.
  4. Explain why increasing the resistance in a circuit decreases the current for a fixed voltage.
  5. A 6 Ω resistor dissipates 12 W of power. Determine the current through the resistor and the voltage across it.
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