Charge and Current Study Guide

Potential difference (p.d.)

Measured in volts (V) and represents the energy transferred per unit charge.

Current (I)

Measured in amperes (A) and represents the rate of flow of charge.

Charge (Q)

Measured in coulombs (C) and represents the quantity of electricity.

Relationship between charge, current, and time

Q = It.

Work done (W) in moving a charge

W = VQ.

Voltmeter

Device connected in parallel to measure potential difference.

Ammeter

Device connected in series to measure current.

In a series circuit, current is

The same throughout the circuit.

In a parallel circuit, potential difference is

The same across each branch.

Conventional current flow

Flows from positive to negative, opposite to electron flow.

Kirchhoff's Current Law

The total current entering a junction equals the total current leaving.

Conductors

Materials that have many free charge carriers (usually electrons).

Insulators

Materials that have few or no free charge carriers.

Semiconductors

Materials that have conductivity between conductors and insulators.

One Coulomb (C)

Equals 1 Ampere-second (A·s).

Energy transferred

Also known as work done.

Potential difference is sometimes called

Voltage.

Cells

Convert chemical energy to electrical energy.

Generators

Convert mechanical energy to electrical energy.

Batteries

Composed of multiple cells.