Capacitance, Current & Resistance

Capacitance

The ability of a system to store electric charge per unit of potential difference (C=Q/V). Measured in Farads (F).

Dielectric

An insulating material that increases a capacitor's ability to store charge by reducing the internal electric field.

Resistivity

An intrinsic property of a material that quantifies how strongly it opposes the flow of electric current.

Electromotive Force (EMF)

The total work done by a source (like a battery) to move a unit charge through a complete circuit.

Drift velocity

The average velocity attained by charged particles (electrons) in a material due to an electric field.

Equivalent Resistance

The single resistance value that could replace a combination of resistors while keeping the same total current and voltage.

If you triple the voltage across a capacitor, by what factor does the stored energy increase?

Energy is proportional to the square of the voltage. If voltage is tripled (3V), the energy becomes 3^2 or 9 times the original value.

Why must the charge (Q) be identical for two different capacitors connected in a single-path series circuit?

Charge is identical because of the Law of Conservation of Charge and the single-path nature of the circuit. Since they are in a single line, the same amount of charge must accumulate on every capacitor in that branch.

Why does the resistance of a metal increase with temperature, while some semiconductors might see a decrease?

In metals, heat makes the positive ions vibrate more, causing more collisions with flowing electrons. In semiconductors, heat provides enough energy to "shake loose" more electrons (charge carriers), which actually improves conductivity and lowers resistance.

If electrons move at only a few millimeters per second (drift velocity), why does a lamp miles away turn on instantly when the circuit is closed?

The Electric Field travels near the speed of light, even though individual electrons are slow.

If you add a fourth identical resistor in parallel to three existing ones, does the total equivalent resistance of the circuit increase or decrease?

The total equivalent resistance decreases.

If a wire is compressed so its length is halved (maintaining constant volume), what happens to its resistance?

The resistance decreases to one-fourth of its original value.

Which one of these changes if you cut a wire in half? Resistance or Resistivity?

Resistance changes; Resistivity stays the same.

What happens to a sum of capacitance in series?

Total C is always less than the smallest individual capacitor

What happens to a sum of capacitance in series?

Total C is simply the sum

What happens to a sum of resistance in parallel?

Total R is always less than the smallest individual resitor.

What happens to a sum of resistance in series?

Total R is the sum

Resistance

Opposition to current flow in a specific component depending on material, shape and size.