Electric current

• 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 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 Current Run Forever in Water?
  Current can continue through water while a complete circuit and electrode reactions are sustained, but real cells eventually change or run out of reactants.
• Does a Capacitor Pass DC Current?
  An ideal capacitor carries current while its voltage changes, such as during DC charging, but carries no current after steady state is reached.
• 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.
• What Is the Electric Field Around a Current-Carrying Conductor?
  A steady current needs a longitudinal electric field inside a resistive wire; the field outside depends on surface charges, voltage, and the return-path geometry.