Physics Test 2 part 1

Question 1

How many volts does a diagnostic imaging department use?

Answer 1

440 volts or less

Question 2

Transformer

Answer 2

is a device that increases or decreases the voltage without the use of any moving parts or any electrical contact between the two circuits and employs the principle of electromagnetic induction.

Question 3

How many coils does a transformer consist of?

Answer 3

2

Question 4

Primary coil

Answer 4

coil hooked up to the power source. A magnetic field is produced here through electromagnetism

Question 5

Secondary coil

Answer 5

coil hooked up to whatever is using the power. Voltage is induced here through electromagnetism

Question 6

Transformer Law Part 1

Answer 6

Deals with changes in voltage
Vs / Vp = Ns / Np
Vs = Secondary Voltage
Vp = Primary Voltage
Ns = Secondary number of coils (turns)
Np = Primary number of coils (turns)

Question 7

Step up transformer

Answer 7

Any transformer that increases the voltage. Have a turns ratio greater than 1. There are more coils on the secondary side vs primary side.

Question 8

Step down transformer

Answer 8

decreases the voltage

Question 9

Transformer Law part 2

Answer 9

Deals with changes in current
Is / Ip = Vp /Vs

Question 10

Why do transformers only operate on AC?

Answer 10

They are designed to work only with alternating currents

Question 11

Air core transformer

Answer 11

The simplest type of transformer consisting of two insulated coils lying side by side with only air separating the coils

Question 12

Open core transformer

Answer 12

An iron core is inserted into each coil of an air core transformer

Question 13

Flux leakage

Answer 13

Magnetic lines are lost from an open core transformer

Question 14

Closed core transformer

Answer 14

The coils are wrapped around an iron square.

Question 15

Shell-type transformer

Answer 15

Both the primary and secondary coils are wrapped around the central section of the core to increase efficiency.
Most efficient but most expensive

Question 16

Autotransformer

Answer 16

A transformer that works on the principle of self induction, because it only has one coil.
Also known as a variable transformer

Question 17

Autotransformer Law

Answer 17

Deals with voltage produced
Vs / Vp = # of tapped turns/ total # of turns

Question 18

What do x-ray machines contain?

Answer 18

at least an autotransformer, a step-up transformer and a step-down transformer.

Question 19

How many possible causes of power loss is there?

Answer 19

4
flux leakage
Copper loss
Eddy current loss
Hysteresis loss

Question 20

Copper loss

Answer 20

Since long lengths of copper wire are used in the construction of a transformer, resistance exists which causes heat.
This can be minimized by having an adequate diameter wire.

Question 21

Eddy current loss

Answer 21

Will occur only when iron is used in the core.
Since iron is a conductor, it is in the changing magnetic field which creates a current within it.
The current will swirl around the iron core

Question 22

Hysteresis loss

Answer 22

Since the magnetic field of the primary coil is continuously changing, the magnetic domains of the iron core must continuously rearrange themselves to the magnetic field.
This increases the motion of the atoms in the core, causing heat

Question 23

How many possible devices are there for current regulation?

Answer 23

4
Rheostat
Choke coil
Saturable reactor
High frequency circuit

Question 24

Rheostat

Answer 24

also called a potentiometer.
A variable resistor is added to the circuit that regulates resistance and therefore current according to Ohm’s Law.
These can be used as mA selectors and in electric timers.

Question 25

Choke coil

Answer 25

Works on the principle of self induction and requires AC to work.
It consists of a coil of wire and an iron core.

Question 26

Saturable reactor

Answer 26

Also known as magnetic amplifiers, saturable reactors use a DC control winding to control the flow of AC current in a circuit.

Question 27

High frequency circuit

Answer 27

A computerized method of current regulation that requires advanced circuitry.