IEM 1-2

A transformer operates based on

Electromagnetic mutual induction

The coil connected to the power source is the

Primary

The induced current appears in the

Secondary

A transformer that increases voltage is

Step-up

A transformer that decreases voltage is

Step-down

Transformers operate using

AC

Normal transformer efficiency is above

95%

I²R loss is known as

Copper loss

I²R loss is minimized using

Low-resistance wire

Power lost in copper becomes

Heat

Hysteresis loss is caused by

Constant magnetizing/demagnetizing

Residual magnetism causes

Hysteresis loss

Hysteresis loss is minimized by using:

Silicon iron

Eddy current loss is due to

Circulating magnetic currents

Eddy current loss is reduced by:

Laminating the core

Air-core transformer uses

No core (air only)

Open-core transformer uses:

Iron inside coils

Closed-core transformer has

A fully sealed magnetic path

Shell-type transformer has:

Primary and secondary wrapped together

Shell-type efficiency improves because:

Coils are very close together

An autotransformer has:

One coil with taps

Autotransformers adjust:

Incoming line voltage

Step-up transformer increases voltage to:

Kilovolts

Filament transformer output is

5–15 V at 3–5 A

High-voltage transformer is needed for:

X-ray production

A capacitor stores

Electrical charge

The insulating layer in a capacitor is the:

Dielectric

Capacitance is measured in:

Farads

Most capacitors use the unit:

Microfarads

A capacitor charges until equal to the:

DC supply voltage

Capacitors provide:

Constant voltage

A capacitor has:

Two metal plates

Rectification converts AC into:

Pulsating DC

A rectifier allows current in:

One direction only

Modern rectifiers use:

Semiconductors

X-ray tubes operate best using:

DC

Backward AC flow causes:

Tube damage

A diode is made of:

p-n junction

Electron flow in diode:

n → p

Conventional current flow:

p → n

n-type material has:

Free electrons

p-type material has

Positive holes

Full-wave rectification uses:

4 diodes

Half-wave rectification uses:

1 diode

Rectification prevents:

Electron backflow

More turns in secondary increases

Voltage

Increasing voltage decreases:

Amperage

Lower secondary voltage means:

Step-down transformer

Laminated cores reduce:

Eddy currents

Filament transformer is used to:

Heat filament

Autotransformer adjusts:

kVp

NOT a transformer type:

Capacitive-core

Induction needs:

Changing magnetic field

Efficiency increases when coils:

Close together

Dielectric must be:

Insulator

Rectifiers stop:

Backflow of electrons

Free electrons belong to:

n-type

Positive holes belong to:

p-type

Capacitors discharge:

In short bursts

HV transformer raises voltage to:

kVp

Smallest negative charge:

Electron

Proton is found in:

Nucleus

Electrification occurs when:

Too many/few electrons

Rubbing objects creates:

Friction

Earth is an:

Electric ground

1 coulomb equals:

6.3 × 10¹⁸ electrons

Like charges:

Repel

Opposite charges:

Attract

Coulomb’s law follows the:

Inverse square law

Charge concentrates on:

Sharp points

Unit of electric potential:

Volt

1 V equals:

J/C

Electric charges in motion:

Electric current

A conductor:

Allows electrons to flow easily

An insulator:

Prevents electron flow

A semiconductor:

Can act as both

Shockley demonstrated semiconductors in:

1946

Example of semiconductor:

Silicon

Superconductors have:

Zero resistance

Ohm’s law:

V = IR

Current is measured in:

Amperes

Resistance measured in:

Ω

Resistance increases when:

Wire thin

Two circuit types:

Series and parallel

DC flows:

One direction

AC flows:

Back and forth

Frequency of AC in PH:

60 Hz

Electric power formula:

P = IV

Electric power measured in:

Watts

Power loss formula:

P = I²R

Electron spin creates:

Magnetic field

Magnetic lines are:

Dipolar

Many aligned dipoles form:

Magnetic domain

Natural magnet:

Earth

Artificial permanent magnets are made of:

Iron

Heating a magnet:

Weakens it

Electromagnet formed by:

Iron core + coil

Nonmagnetic materials:

Not affected by magnets

Diamagnetic materials:

Weakly repelled

Paramagnetic materials:

Weakly attracted