Section 9.8: Review Examples

This section reviews key concepts from Electric Forces, Electric Potential, Capacitance, Current, Resistance, Ohm's Law, Kirchhoff Laws, and Magnets & Magnetic Fields. Work through these examples to reinforce understanding.

Example 1: Electric Force

Two charges, \(q_1 = 2 \, \mu C\) and \(q_2 = 3 \, \mu C\), are 0.5 m apart in vacuum. Find the force between them.

Use Coulomb's law: \( F = k \frac{q_1 q_2}{r^2} = 9\times10^9 \frac{(2\times10^{-6})(3\times10^{-6})}{0.5^2} = 0.216 \, \text{N} \)

Example 2: Magnetic Force on a Wire

A 0.4 m long wire carries a 5 A current perpendicular to a 0.2 T magnetic field. Find the force on the wire.

\( F = I L B = 5 \times 0.4 \times 0.2 = 0.4 \, \text{N} \)

Example 3: Potential Difference

A 12 V battery is connected across a 6 Ω resistor. Find the current through the resistor.

Ohm's Law: \( I = V / R = 12 / 6 = 2 \, \text{A} \)

Practice Problems

  1. Find the force on a 5 μC charge placed 0.3 m from a 2 μC charge.
  2. A 10 μF capacitor is connected to a 12 V battery. Find the stored charge.
  3. A wire of length 0.6 m carries 3 A current perpendicular to a 0.1 T magnetic field. Find the force.
  4. Two resistors, 6 Ω and 12 Ω, are in series across a 18 V battery. Find the current.
  5. A proton moves at 2 × 10^6 m/s perpendicular to a 0.3 T field. Find the magnetic force.
← Previous Next →