Cards | 10 |

Topics | Battery Configurations, Current, Direct Current (DC), Inductors, Integrated Circuits, Resistance, Resistors, Semiconductors, Voltage |

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.

Direct current flows in only one direction in a circuit, from the negative terminal of the voltage source to the positive. A common source of direct current (DC) is a battery.

An inductor is coiled wire that stores electric energy in the form of magnetic energy and resists changes in the electric current flowing through it. If current is increasing, the inductor produces a voltage that slows the increase and, if current is decreasing, the magnetic energy in the coil opposes the decrease to keep the current flowing longer. In contrast to capacitors, inductors allow DC to pass easily but resist the flow of AC.

Circuits containing transistors are packaged into **integrated circuit** chips that allow encapsulating complex circuit designs (CPU, memory, I/O) for easier integration into electronic devices and machines.

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.

Semiconductors have valence shells that are exacly half full and can conduct electricity under some conditions but not others. This property makes them useful for the control of electrical current.

Voltage (V) is the electrical potential difference between two points. Electrons will flow as current from areas of high potential (concentration of electrons) to areas of low potential. Voltage and current are directly proportional in that the higher the voltage applied to a conductor the higher the current that will result.