Electric Circuits

• What is electric current (I)?

  The rate of flow of charged particles

  
• What does potential difference (V) represent?

  Energy transferred per unit charge
• How is electric current calculated?

  By dividing change in charge by change in time
• How is potential difference calculated?

  By dividing energy transferred by charge
• What is resistance (R)?

  A measure of difficulty for charge carriers
• How is resistance calculated?

  By dividing potential difference by current
• What does Ohm's law state about current and potential difference?

  Current is directly proportional to potential difference
• What does the principle of charge conservation state?

  Total electric charge in a closed system does not change
• What does Kirchoff's first law state about current at a junction?

  Total current in equals total current out
• How does current behave in series and parallel circuits?

  • Series circuit: Current is the same everywhere
  • Parallel circuit: Sum of currents equals total current
• What does the principle of conservation of energy state?

  Energy cannot be created or destroyed
• What does Kirchoff's second law state about voltages in a circuit?

  Sum of voltages in series equals battery voltage
• How does potential difference distribute in series and parallel circuits?

  • Series circuit: Battery p.d is shared across elements
  • Parallel circuit: Potential difference across each branch is the same
• What is the formula for total resistance in a series circuit?

  RT = R1 + R2 + R3 + ...
• How do you derive the total resistance formula for a series circuit?

  By applying Ohm's law and Kirchoff's second law
• What is the formula for total resistance in a parallel circuit?

  1/RT = 1/R1 + 1/R2 + 1/R3 + ...
• How do you derive the total resistance formula for a parallel circuit?

  By applying Kirchoff's second law and Ohm's law
• What is the formula for energy transferred?

  W = Pt
• How can you find the current using power and voltage?

  I = P / V
• What are the derived formulas for power using Ohm's law?

  P = VI, P = I^2R, P = V^2/R
• What are the properties of current-voltage graphs for different components?

  • Ohmic conductor: Straight line through origin
  • Semiconductor diode: Forward and reverse bias behavior
  • Filament bulb: Curves due to increasing resistance
  • Thermistor: Resistance decreases with increasing temperature

  
• What is resistivity (ρ)?

  A measure of how easily a material conducts electricity
• How is resistivity defined mathematically?

  ρ = RA / l
• How can you calculate resistance using resistivity?

  R = ρl / A
• What factors affect current in a conductor?

  Charge carrier density, drift velocity, charge
• What is the charge of a single electron?

  $1.6 \times 10^{-19} C$
• How is current calculated in a conductor?

  I = nqvA
• How does charge carrier density change with temperature?

  • More energy increases charge carrier density
  • Higher temperatures release more charge carriers

  
• What happens to charged particles in a conductor?

  They constantly collide and do not travel straight.
• What is the average speed of charged particles in a conductor called?

  Drift velocity (v)
• What is the charge (q) of a single electron?

  $1.6 \times 10^{-19} C$
• How can current (I) through a conductor be calculated?

  Using the formula $I =$$nqvA$
• What does the variable 'n' represent in the current formula?

  Charge carrier density
• Why do different materials have different charge carrier densities?

  Due to energy affecting charge carriers' release
• What is the relationship between temperature and charge carrier density?

  Higher temperature increases charge carrier density

  
• What does the resistivity of a material indicate?

  It indicates how strongly a material opposes current
• How does the length of a wire affect its resistance?

  Resistance increases as the length increases
• What does Ohm's law state about voltage and resistance?

  Voltage increases as resistance increases
• What is a potential divider circuit used for?

  To produce a fraction of the source potential
• How can a potential divider supply a variable potential difference?

  By using a variable resistor in series