Questions | 5 |

Topics | Battery Configurations, Current, Resistance, Resistors, Transformers |

Batteries can be connected together in various combinations to increase their total voltage and/or total current. Connecting batteries in **series** combines their voltage while keeping their current the same, connecting batteries in **parallel** combines their current while keeping their voltage the same, and using a **series-parallel** configuration, half the batteries can be connected in series and half in parallel to combine both voltage and current.

Current is the rate of flow of electrons per unit time and is measured in **amperes** (A). A **coulomb** (C) is the quantity of electricity conveyed in one second by a current of one ampere.

Resistance is opposition to the flow of current and is measured in **ohms** (Ω). One ohm is defined as the amount of resistance that will allow one ampere of current to flow if one volt of voltage is applied. As resistance increases, current decreases as resistance and current are inversely proportional.

Resistors are used to limit voltage and/or current in a circuit and can have a **fixed** or **variable** resistance. Variable resistors (often called potentiometers or rheostats) are used when dynamic control over the voltage/current in a circuit is needed, for example, in a light dimmer or volume control.

A transformer utilizes an inductor to increase or decrease the voltage in a circuit. AC flowing in a coil wrapped around an iron core magnetizes the core causing it to produce a magnetic field. This magnetic field generates a voltage in a nearby coil of wire and, depending on the number of turns in the wire of the **primary** (source) and **secondary** coils and their proximity, voltage is induced in the secondary coil.