QA3 Preparation

• What happens when like charges interact?

  They repel each other.
• What happens when unlike charges interact?

  They attract each other.
• What does the law of conservation of charge state?

  Charge cannot be created or destroyed.
• What happens to an object that gains electrons?

  It becomes negatively charged.
• What happens to an object that loses electrons?

  It becomes positively charged.
• How does Coulomb's Law describe the force between two charges?

  It is proportional to the product of charges.
• What is the formula for the force between two charges?

  $F =$$k \frac{q_1 q_2}{r^2}$
• What occurs when a positively charged object is near a neutral object?

  It attracts negative charges in the neutral object.
• What happens to a neutral object in an electric field?

  It polarizes, creating a dipole.
• What direction does the electric field point for a negative charge?

  Inward.
• What direction does the electric field point for a positive charge?

  Outward.
• How does electric field strength change with distance?

  It is inversely proportional to the square of the distance.
• If the distance from a charge is doubled, what happens to the field strength?

  It becomes one-fourth.
• How does the electric field of a uniformly charged line differ from point charges?

  It depends on the distance from the line.
• What is the formula to calculate electric field magnitude?

  $E =$$\frac{kq}{r^2}$
• What does Ohm's Law define?

  The relationship between voltage, current, and resistance.
• What is the formula for Ohm's Law?

  $V =$$IR$
• What happens to current if resistance increases while voltage is constant?

  Current decreases.
• What happens to current if voltage increases while resistance is constant?

  Current increases.
• What does Kirchhoff's Current Law state?

  Total current entering equals total current leaving.
• What is the mathematical expression for Kirchhoff's Current Law?

  $\sum I_{\text{in}} =$$\sum I_{\text{out}}$
• What does Kirchhoff's Voltage Law state?

  The sum of voltage drops equals total voltage supplied.
• What is the mathematical expression for Kirchhoff's Voltage Law?

  $\sum V =$$0$
• How is total resistance calculated in series circuits?

  It is the sum of individual resistances.
• What is the current behavior in series circuits?

  Current is the same through each resistor.
• What happens to voltage drops in series circuits?

  They add up to the total voltage.
• How is total resistance calculated in parallel circuits?

  Using the reciprocal formula.
• What is the formula for total resistance in parallel circuits?

  $\frac{1}{R_{\text{total}}} =$$\frac{1}{R_1} +$$\frac{1}{R_2} +$$\frac{1}{R_3}$
• What happens to current in parallel circuits?

  Current divides among branches.
• What effect does adding resistors in series have on total resistance?

  Total resistance increases.
• What effect does adding resistors in parallel have on total resistance?

  Total resistance decreases.
• What happens to the lighting system in parallel if one bulb burns out?

  Others stay on.
• What are the key concepts of electric charges and Coulomb's Law?

  • Like charges repel, unlike charges attract.
  • Charge is conserved.
  • Negatively charged objects gain electrons.
  • Positively charged objects lose electrons.
  • Coulomb's Law relates force to charge and distance.
• What are the key concepts of electric fields?

  • Electric field direction depends on charge sign.
  • Field strength is inversely proportional to distance squared.
  • Uniformly charged lines have different field behavior.
  • Electric field magnitude can be calculated.
• What are the key concepts of Ohm's Law?

  • Defines relationship between voltage, current, and resistance.
  • Increasing resistance decreases current.
  • Increasing voltage increases current.
• What are Kirchhoff's Laws?

  • KCL: Total current in equals total current out.
  • KVL: Sum of voltage drops equals total supplied voltage.
• What are the characteristics of series and parallel circuits?

  • Series: Total resistance is sum, current is same, voltage drops add up.
  • Parallel: Total resistance decreases, current divides, one bulb burning out doesn't affect others.