Electricity Basics

Voltage

Electrical potential difference, or electrical “push,” between two points; measured in volts (V). Memory

Current

Flow or movement of electrons through a circuit; measured in amperes (A). Memory

Resistance

Opposition to electron flow through a circuit; measured in ohms (Ω).

Ohm’s law

V = I × R; voltage equals current multiplied by resistance.

What happens to current if voltage increases while resistance stays the same?

Current increases.

AC

Alternating current; current repeatedly changes direction and magnitude.

DC

Direct current; current flows in only one direction.

Why do transformers require AC?

AC produces a continuously changing magnetic field, which is necessary for electromagnetic induction.

Electromagnetic induction

Production of voltage in a conductor when it is exposed to a changing magnetic field.

Why does the x-ray tube require one-direction current?

Electrons must travel from the cathode toward the anode; reverse electron flow must be prevented.

Rectification

Conversion of AC into one-direction, pulsating current so current through the x-ray tube flows only from cathode to anode.

Diode

One-way electrical device that permits current flow in one direction and blocks it in the opposite direction; used for rectification.

Half-wave rectification

Uses one half of each AC cycle and blocks the opposite half. Memory

Full-wave rectification

Uses both halves of the AC cycle by reversing the unwanted half so current continues in the same direction.

What is the major advantage of full-wave over half-wave rectification?

Both halves of the AC cycle are used, producing more efficient and continuous x-ray output.