Worksheet 5-7 The Transformer

A transformer with a turns ratio of 1000:1 is: a. A step-down transformer b. A step-up transformer c. An autotransformer d. Used to increase current e. Used to reduce voltage

a. A step-down transformer

An autotransformer: a. Contains a single coil that serves as both primary and secondary coils b. Controls X-ray tube current c. Is a shell type of transformer d. Is an electromechanical device e. Is used to control frequency

a. Contains a single coil that serves as both primary and secondary coils

Which of the following accurately represents the transformer law? a. Is/Ip = Np/Ns b. Is/Ip = Ns/Np c. Is/Ip = Vs/Vp d. Ip/Is = Vp/Vs e. Ip/Is = Np/Ns

a. Is/Ip = Np/Ns

The turns ratio is defined as: a. Number of secondary windings ÷ primary windings b. Primary iron core ÷ secondary iron core c. Primary voltage ÷ secondary voltage d. Primary windings ÷ number of secondary windings e. Secondary current ÷ primary current

a. Number of secondary windings ÷ primary windings

Primary to secondary coupling in a transformer is enhanced by: a. 60 Hz b. AC c. An iron core d. DC e. EMP

c. An iron core

Which of the following statements about transformers is correct? a. If there were equal numbers of primary and secondary coil turns, the turns ratio would be zero. b. In the shell-type transformer, the primary and secondary coils are wound on different cores. c. Laminated transformer cores are more efficient than unlaminated ones. d. The autotransformer controls current. e. The high-voltage transformer in an X-ray imaging svstem is the autotransformer.

c. Laminated transformer cores are more efficient than unlaminated ones.

When a step-up transformer is in use: a. The primary winding has more turns than the secondary winding. b. The secondary current is greater than the pri mary current. c. The secondary voltage is greater than the primary voltage. d. X-ray tube current is selected. e. The turns ratio is equal to 1.

c. The secondary voltage is greater than the primary voltage.

If a transformer produces a large secondary current from a small primary current: a. Power will be increased. b. The turns ratio will be greater than 1. c. The turns ratio will be less than 1. d. The voltage will be larger on the secondary side than on the primary side. e. There will be more windings on the secondary side than on the primary side.

c. The turns ratio will be less than 1.

The principal application of a transformer in an X-ray imaging system is to: a. Change AC to DC b. Change DC to AC c. Change frequency d. Change voltage e. Produce x-rays

d. Change voltage

When a transformer is designed, the change in current is: a. Dependent on the supply voltage b. Directly proportional to the voltage change C. In the same direction as the voltage change d. Inversely proportional to the turns ratio e. Proportional to the turns ratio

d. Inversely proportional to the turns ratio

A transformer operates: a. On AC but not on DC b. On both DC and AC c. On DC but not on AC d. Only above its critical current e. Only on a constant voltage

d. Only above its critical current

The output current in a step-up transformer is: a. Higher than the input current b. Independent of the input current c. Independent of the turns ratio d. Lower than the input current e. The same as the input current

d. lower than the input current

Transformers have iron cores to intensify the: a. Electric current b. Electric potential c. Electric power d. Electric voltage e. Magnetic field

e. Magnetic field

If DC is applied to the primary coil of a step-up transformer, what is the result in the secondary coil? a. AC b. Increased current c. Increased magnetic field d. Increased voltage e. Nothing

e. Nothing

Which of the following is a transformer design used in X-ray imaging systems? a. Capacitor type b. Filament type c. Rectifier type d. Rotating type e. Shell type

e. Shell type

A transformer "transforms" or changes electric: a. Frequency b. Impedance c. Power d. Resistance e. Voltage

e. Voltage