Electrical resistance

• How Do You Combine Three Resistors in Parallel?
  For three resistors connected across the same two nodes, add their reciprocals, then invert the sum to get the equivalent resistance.
• How Does a Resistor “Know” to Increase the Voltage Across It?
  A resistor does not sense or choose its voltage: the circuit’s source, resistance, current, and electric fields determine the potential difference.
• How Does Resistance Relate Voltage to Current?
  Resistance does not create current; it relates current to voltage. Use Ohm’s law for an ohmic resistor and include the rest of the circuit.
• Why Is Current the Same in a Series Circuit?
  In a steady series circuit, charge conservation makes the current equal through every component; voltage drops differ according to each component’s resistance.
• How Does a Cell’s Internal Resistance Vary With Temperature?
  A cell’s internal resistance usually falls as temperature rises because its electrolyte conducts better, but the trend depends on chemistry and conditions.
• How Can a Potential Divider Set a Component’s Voltage to Zero?
  A potential divider can set a load’s voltage to zero by placing its wiper at ground; a series variable resistor usually only approaches zero current.
• Does Electricity Take the Path of Least Resistance?
  Electricity does not choose only the least-resistance route. Learn how current divides between branches and how circuit laws determine each path.
• What Is Equivalent Resistance?
  Equivalent resistance is the resistance a single resistor would need to match a network’s voltage–current behavior at specified terminals.
• What Is the Difference Between I²R, V²/R, and VI for Power?
  VI is the general circuit-power formula; I²R and V²/R come from Ohm’s law for a resistor, using its voltage and current.
• How to Calculate a Voltmeter Reading
  Calculate a voltmeter reading by identifying its connection points, finding the voltage difference between them.
• Can Electrical Resistance Depend on Direction?
  Ordinary linear resistors have the same resistance when current reverses, but anisotropic materials and nonlinear devices can behave differently.
• What Is a Voltage Drop in a DC Circuit?
  Learn what voltage drop means in a DC circuit, how to calculate it with Ohm’s law, and how drops behave in series and parallel circuits.