TRANSFORMERS 3

What is a transformer?

A device that changes current and voltage, converting low voltage to high voltage or vice versa.

Why is high voltage needed in radiography?

High voltage is required for X-rays to penetrate the patient effectively.

How does a transformer transfer energy?

By using magnetic fields to transfer electrical energy from one circuit to another through electromagnetic induction.

What are the four types of transformers?

Air core, open core, closed core, and shell type transformers.

What is an air core transformer?

Two solenoids placed close together without an iron core.

What is an open core transformer?

Two solenoids each with an iron core, which concentrates magnetic lines of force and gives a cleaner magnetic field.

What is a closed core transformer?

An iron core that connects both sides of the coil from top to bottom to improve magnetic flux linkage.

What is a shell type transformer?

Both the primary and secondary coils are wrapped around a central laminated iron core.

Which type of transformer is the least efficient?

The air core transformer.

Which type of transformer is the most efficient?

The shell type transformer.

Why are transformer cores made of laminated iron instead of solid iron?

To reduce heat buildup, minimize energy loss, and lower electrical resistance, improving efficiency.

How is EMF (electromotive force) induced in a transformer?

The changing magnetic field in the primary coil induces EMF in the secondary coil.

What determines the induced EMF in a transformer?

The number of turns (coils) on the primary and secondary sides.

What is a step-up transformer?

A transformer that increases voltage and decreases current; the secondary coil has more turns than the primary coil.

What is a step-down transformer?

A transformer that decreases voltage and increases current; the secondary coil has fewer turns than the primary coil.

What does the transformer law state?

The voltage change between the primary and secondary coils is directly proportional to the turns ratio.

What is the turns ratio formula?

Turns ratio = Ns / Np (number of turns in secondary divided by number of turns in primary).

According to the law of conservation of energy, how do voltage and current behave in a transformer?

Power in equals power out; if voltage increases, current decreases proportionally.

What is an autotransformer?

A type of transformer that uses a single coil with self-induction; the same coil acts as both primary and secondary.

What is another name for an autotransformer?

A variable transformer.

What is the main function of an autotransformer in X-ray circuits?

To send a precise voltage to the primary side of the step-up transformer.

How does an autotransformer mathematically act compared to mutual transformers?

It follows the same principles, using the ratio of turns to determine voltage changes.

What happens if the number of tapped turns is decreased in an autotransformer?

It reduces the voltage on the secondary side.

What happens if the number of tapped turns is increased in an autotransformer?

It increases the voltage on the secondary side.

What is the autotransformer law formula?

Vs / Vp = Ns / Np (secondary voltage divided by primary voltage equals secondary turns divided by primary turns).

How does an autotransformer operate?

It uses self-induction, where part of a single coil’s winding acts as both the input (primary) and output (secondary).

Why is the autotransformer important in X-ray machines?

It provides variable and accurate control of the voltage supplied to the X-ray tube.

How can a turn ratio be expressed?

As a fraction, as a whole number, or as a ratio.

How is the turn ratio 20 to 5 expressed as a fraction?

4

How is the turn ratio 20 to 5 expressed as a whole number?

4:1

What does a step-up transformer do?

Increases voltage and decreases current.

What is the turns ratio of a step-up transformer?

Greater than 1 (e.g., 6:1).

In a step-up transformer, how do voltage and current change?

Voltage increases; current decreases.

What does a step-down transformer do?

Decreases voltage and increases current.

What is the turns ratio of a step-down transformer?

Less than 1 (e.g., 0.5:1).

In a step-down transformer, how do voltage and current change?

Voltage decreases; current increases.

What is the transformer law for voltage?

Voltage is directly proportional to the turns ratio.

What is the formula for the transformer law for voltage?

Vs / Vp = Ns / Np

What is the transformer law for current?

Current is inversely proportional to the turns ratio.

What is the formula for the transformer law for current?

Is / Ip = Np / Ns

If the turns ratio increases, what happens to voltage?

Voltage increases proportionally.

If the turns ratio increases, what happens to current?

Current decreases inversely.

If the turns ratio decreases, what happens to voltage?

Voltage decreases proportionally.

If the turns ratio decreases, what happens to current?

Current increases inversely.