PHYSICS

Question 1

What is the purpose of the line voltage compensator in the low voltage circuit?

Answer 1

• to automatically adjust the incoming voltage to 220 volts

* incoming voltage to X-ray equipment must be alternating!

Question 2

What is the purpose of the autotransformer (kvp selector) in the low voltage circuit?

Answer 2

• supplies voltage of varying magnitudes to the filament and high voltage circuits
• acts as both a step up and step down transformer
• operates on self induction

Question 3

What is the purpose of the pre reading voltmeter in the low voltage circuit?

Answer 3

-gives you an indication of what the desired kvp will be

Question 4

What is the purpose of the exposure timer and switch on the low voltage circuit?

Answer 4

-the device that activates a switch to open and close the circuit, allowing current to flow thru the X-ray tube

Question 5

What is the purpose of the mA selector in the low voltage circuit?

Answer 5

-as mA is increased, the filament becomes hotter and thermionic emission increases

Question 6

Define rheostat:

Answer 6

• a device that controls the current to the filament by varying the amount of resistors included in the filament circuitry
• main control of mA
• more resistors=less current (aka mA)

Question 7

What is the function of the ammeter?

Answer 7

-measure the filament current (mA)

Question 8

What is the space charge region?

Answer 8

-due to the space charge around the filament, an increase in kvp causes a subsequent rise in mA because more electrons per second are driven to the anode (undesirable)

Question 9

What is the function of the step up transformer in the high voltage circuit?

Answer 9

• consists of many turns of wire to “step up” the voltage from the primary circuit
• turns ratio is about 500:1

Question 10

What is the function of the milliammeter (mA meter) in the high voltage circuit?

Answer 10

-to measure the current (mA) as it passes thru the X-ray tube during the actual exposure

Question 11

What is the function of the rectifier in the high voltage circuit?

Answer 11

• converts AC to DC
• the current supplied to the high voltage transformer is AC, therefore a device must be placed to convert to DC since the X-ray tube cannot function properly on AC

Question 12

What is the function of the X-ray tube in the high voltage circuit?

Answer 12

-when the exposure switch is activated (closed), current is allowed to pass thru the X-ray tube for X-ray production