• 15 parts
  • Checked September 2026

X-Ray Circuit Diagram, Labeled

The basic X-ray machine circuit: twelve components in the primary, secondary and filament circuits.

X-Ray Circuit Diagram, Labeled

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
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Write the name of each numbered part.Answer key

  1. X-ray tube
  2. Step-up transformer (high-voltage)
  3. Autotransformer
  4. Rectifier
  5. Main switch
  6. Timer
  7. Circuit breaker
  8. Voltmeter (prereading kilovoltmeter)
  9. Milliammeter
  10. Rheostat
  11. Filament ammeter
  12. Step-down transformer (filament)
  13. Primary circuit (low-voltage)
  14. Secondary circuit (high-voltage)
  15. Filament circuit

Own drawing from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

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All 15 parts on the diagram

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Components 12

  1. X-ray tube Where the X-rays are made, between cathode and anode.
  2. Step-up transformer (high-voltage) Raises the voltage to the thousands of volts the tube needs.
  3. Autotransformer One coil with a moving tap. It selects the voltage.
  4. Rectifier Changes alternating current to direct current for the tube.
  5. Main switch Connects the machine to the power supply.
  6. Timer Starts and stops the current to the step-up transformer.
  7. Circuit breaker Opens the circuit if too much current flows.
  8. Voltmeter (prereading kilovoltmeter) Shows the tube voltage that is set, before it is applied.
  9. Milliammeter Measures the current through the X-ray tube.
  10. Rheostat A variable resistor. It sets the filament current.
  11. Filament ammeter Measures the current that heats the filament.
  12. Step-down transformer (filament) Lowers the voltage for the filament of the tube.

The three circuits 3

  1. Primary circuit (low-voltage) Everything between the power supply and the primary coil.
  2. Secondary circuit (high-voltage) The secondary coil and everything joined to it.
  3. Filament circuit Supplies the current that heats the filament.

How this list was compiled: Every name checked on 2026-09-30 and kept only where both of these use it. (1) US War Department, TM 8-280, Military Roentgenology (1944), a public-domain training manual, full text at https://archive.org/details/unitedstates_militaryroentgenology_1944 : main switch, autotransformer, prereading voltmeter, timer, circuit breaker, step-up (high tension) transformer, rectifiers, milliammeter at the midpoint of the secondary, the filament circuit with its regulator (a choke coil or a rheostat), filament ammeter and filament transformer. (2) J. Selman, The Fundamentals of X-ray and Radium Physics, fifth edition (1972), a textbook for radiologic technologists, chapter X-ray Circuits, full text at https://archive.org/details/B-001-014-315 : the primary circuit (main switch, autotransformer, prereading kilovoltmeter, timer, circuit breaker, the filament circuit with its rheostat, step-down transformer and filament ammeter, the primary coil) and the secondary circuit (secondary coil, milliammeter, rectifier, X-ray tube). Licence: own work

The drawing: Own drawing from plain geometry; nothing traced. Licence: own work

How it works

This X-ray circuit diagram is labeled in three panels, one for each circuit of a basic X-ray machine: the primary circuit, the secondary circuit and the filament circuit. Twelve components sit where they are wired.

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Primary and secondary

Power enters at the main switch. The autotransformer selects a voltage, the voltmeter shows it, and the timer passes it to the step-up transformer. On the high-voltage side the rectifier changes the current to direct current for the X-ray tube.

The filament circuit

A second, low-voltage path heats the filament of the tube. The rheostat sets its current, the filament ammeter shows it, and the step-down transformer lowers the voltage.

  • Three dials, no letters: the voltmeter bridges two wires, the milliammeter sits mid-way on the secondary coil, the filament ammeter is in the bottom panel.

Questions and answers

What are the three circuits of an X-ray machine?

The primary or low-voltage circuit, from the power supply to the primary coil of the step-up transformer; the secondary or high-voltage circuit, from the secondary coil to the X-ray tube; and the filament circuit, which heats the filament of the tube.

What does the autotransformer do in an X-ray circuit?

It selects the voltage sent to the primary coil of the step-up transformer. Moving its tap changes that voltage, and so the kilovoltage across the tube.

Where is the milliammeter in an X-ray circuit?

In the secondary circuit, in series with the tube. It is connected at the midpoint of the secondary coil, which is grounded, so the meter can sit safely on the control panel.

Why does an X-ray machine have two transformers?

The step-up transformer raises the voltage for the tube. The step-down transformer lowers the voltage for the filament, and keeps the low-voltage side apart from the high voltage.

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