ELE 100 Exam 3

Transistor is a ___________________________.

3-terminal device

A transformer which has 1380 turns in its primary coil is to be used to convert the mains voltage of 230 V to operate a 6 V bulb. How many turns should the secondary coil of this transformer have?

36 turns

AC frequency in US(United States);

60 Hz

What are the effects of moving a closed wire loop through a magnetic field?

A voltage is induced in the wire, a current is induced in the wire and the polarity of the voltage across the wire depends on the direction of motion

Will a transformer work with direct current (d.c.) or alternating current (a.c.)?

AC only

What would result in greater magnetic field around a coil of wire?

Adding more loops of wire

Which amongst the following choices listed below is NOT attracted to a magnet.

Aluminum

You can tell if an object is magnetic if the groupings of atoms:

Are lined up in the same direction

The terminals of a BJT transistor are called;

Base, Collector and Emitter

Commonly used transistor/s is/are ________________________.

Both A & B

Ammeter measures ___________________.

Current

_________________is the is the generation of current due to relative motion between a wire and a magnetic field.

Electromagnetic Induction

What is it that does not affect the amount of current flow induced by magnetism?

Environment

A light emitting diode absorbs light to generate electricity.

False

Ammeters are always connected in parallel in a circuit for measuring the currents

False

An electromagnet is a permanent magnet

False

Current does not flow in a forward biased diode

False

Diode conducts in both directions

False

Integrated circuits are devices made up of only resistors.

False

Like charges attract each other

False

Step-up transformers are located near to end user

False

The heavier the doping in a semiconductor, lower is the conductivity.

False

The magnetic field strength is weakest at the poles and strongest along the length of the magnet.

False

When you break a magnet into two, you can separate the two poles

False

Unit of Inductance is _________________.

Henry

Naturally occurring magnets in nature are called:

Lodestones

This is a force where objects are attracted or repelled to one another

Magnetism

Electrical Generator performs which kind of energy conversion?

Mechanical Energy to Electrical Energy

MOSFET stands for

Metal Oxide Semiconductor Field Effect Transistor

Who discovered the operating principle of electromagnetic generators?

Michael Faraday

The machine that converts electrical energy to mechanical energy is called a:

Motor

What causes magnetism?

Movement of electrons around the nucleus and spinning around their own axis.

Identify the non-renewable energy resource

Nuclear

Chain reaction can be seen in ____________.

Nuclear Power Plant

What is meant by a step down transformer?

One where the output voltage is SMALLER than the input voltage

Converting AC to DC is accomplished by the process of ___________________.

Rectification

Ohmmeter measures________________________.

Resistance

How do you make an electromagnet?

Run current through a wire wrapped around an iron rod

Identify the semiconductor

Silicon

In a transformer, the primary coil has twice as many loops as the secondary coil. This is a __________ transformer

Step-down

A transistor is used for

Switching voltages & currents and also for amplifying small signals into large currents.

An object is not magnetized if

The groupings of atoms are scattered

The faster the coil of a generator rotates through the magnetic field the______________.

The higher the output voltage

What happens when you turn off the current in an electromagnet?

The magnetism is turned off

A P-type semiconductor material has a shortage of electrons with vacancies called holes

True

According to principle of electro-magnetic induction, generator produces voltage when there is a changing magnetic field

True

Addition of impurities to the pure semiconductor is called Doping.

True

For a transformer, power is conserved at the primary (imput) and the secondary (output).

True

Increasing the current flowing through a coil increases the magnetic field strength.

True

Inductor is an element which is a coil of wire wound around an iron core

True

Inductors add up like resistors in series and parallel.

True

Magnetic flux flows from the North Pole to the South Pole

True

Materials that loose magnetism quickly are called "Soft Magnets"

True

Organic LED's give off very nice vibrant colors and are flexible

True

Semiconductors are materials that have conductivity in between conductors and insulators.

True

The operation of an electrical generator relies on electromagnetic induction

True

The size of an integrated circuit is part of the reason for the importance of ICs in electronics.

True

The two basic multi-meters are analog and digital

True

Voltmeters and Ammeters are polarized instruments

True

When using an analog meter to measure unknown currents or voltages, always start with the range selector switch set at the highest position

True

How can you show that electricity creates a magnetic field?

Use a compass near a wire with current flowing through it

A ferromagnetic material is:

a material that shows strong magnetic effects

A magnet made of a material that keeps its magnetism is known as a

a permanent magnet

AC generators are also called _______________, since they produce an alternating current

alternators

The positive end of a diode is called the ____________ and the negative end is called the _____________.

anode and cathode

Increasing the number of turns of wire on the secondary of a transformer will___________.

decrease the secondary current and increase the primary current

Advantages of digital meters over analog meters are_________________.

display, accuracy and no ambiguity

An N-type semiconductor has excess of

electrons

An P-type semiconductor has excess of ______________.

holes

Electromagnetic induction is a term used to describe___________.

production of electric potential due to change in magnetic flux

If two magnets were in this order: NS-SN they would:

repel

When the current through a coil reverses direction, the magnetic field around the coil

reverses its direction

When the current through a coil reverses direction, the magnetic field around the coil _____.

reverses its direction

An integrated circuit is made on a ______________piece of Silicon called the chip.

single

Which of the following are magnetic materials

steel and iron