Comprehensive Notes on Current, Voltage, and Resistance

Current, Voltage, and Resistance

Current (I)

  • The rate of flow of electric charge (electrons).
  • Unit: Ampere (A)

Voltage (V)

  • The ratio of the work needed to move a charge to the strength of that charge.
  • Unit: Volt (V)

Resistance (R)

  • The opposition to the flow of an electric current.
  • Unit: Ohm (\Omega)

Factors Affecting Resistance

  • LENGTH: Resistance increases as length increases.
  • AREA: Resistance increases as cross-sectional area decreases.
  • TEMPERATURE: Resistance increases as temperature increases.

Ohm’s Law

  • Ohm's law describes the relationship between current, voltage, and resistance in a circuit.
  • The potential difference (V) is directly proportional to the current intensity (I) and resistance (R).
  • Formula: V = I \times R

Ohm's Law - Formulas

  • V = I \times R
  • I = \frac{V}{R}
  • R = \frac{V}{I}

Example 1

  • Problem: A radio uses a standard 1.5 V battery. How much resistance is in the circuit if it uses a current of 0.01 A?
  • Solution:
    • R = \frac{V}{I}
    • R = \frac{1.5 V}{0.01 A}
    • R = 150 \Omega

Example 2

  • Problem: An electric heater works by passing a current of 100 A through a coiled metal wire, making it red hot. If the resistance of the wire is 1.1 ohms, what voltage must be applied to it?
  • Solution:
    • V = I \times R
    • V = (100 A) \times (1.1 \Omega)
    • V = 110 V

Exercises

  1. Find the applied voltage of a circuit that draws 0.2 amperes through a 4800-ohm resistance.
  2. What current flows through a hair dryer plugged into a 110 Volt circuit if it has a resistance of 25 ohms?
  3. A sensor uses 2.0 \times 10^{-4} A of current when it is operated by a 3.0-V battery. What is the resistance of the sensor circuit?