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Physics Module Form 5 Chapter 4- Electronics GCKL 2010

4-1

UNDERSTANDING THE USES OF THE CATHODE RAY

O S C I L L O S C O P E ( C . R . O . )

What is

thermionic

emission? __________________________________________________________________________________

(a) Label the figure of a vacuum tube:

(b) ………… emitted are accelerated ………….. the anode by the high ……………………

between the cathode and anode.

What is cathode

rays?

A beam of electrons moving at high speed in a vacuum

Properties of Cathode Rays

1. What is the characteristics of the cathode rays?

(i) ……………………………………………………………………..

(ii) …………………………………………………………………….

(iii) ……………………………………………………………………

What it working

principle of the

cathode ray

oscilloscope ?

Structure of the Cathode Ray Oscilloscope

1. Label all parts of Cathode Ray Oscilloscope below.

4.1

Figure 9.1

.


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4-2

2. Fill in the blank all components and its functions.

Figure 9.3


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4-3

What is the

energy change?

eV changeEnergyPotential

The principle of conservation of energy is the change of ____________ electric energy to ________

energy.

eV mv 2

2

1,

How to measure

voltage?

How to measure

short time

intervals?

To measure a D.C voltage:

The unknown voltage, V = (Y-gain) × h

To measure a A.C voltage:

Peak-to-peak voltage, V pp = (Y-gains) × h

Peak voltage, V p = (Y-gains)2

1 (h)

Short time intervals, t = no. of divisions between two pulses × time-base value.

Examples

1. The diagram shows the trace on the screen of a CRO when an a.c voltage is connected to the

Y-input. The Y-gain control is set at 2 V/div and the time base is off.

Calculate the value of :

(a) Peak-to-peak voltage, V pp

(b)Peak voltage, V p.

Solution:

2. An ultrasound signal is transmitted vertically down to the sea bed. Transmitted and reflected

signals are input into an oscilloscope with a time base setting of 150 ms cm-1. The diagram

shows the trace of the two signals on the screen of the oscilloscope. The speed of sound in

water is 1200 ms-1. What is the depth of the sea?

Solution:

2

2

1changeEnergyKinetic mv

Figure 9.11


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4-4

4.2 UNDERSTANDING SEMICONDUCTOR DIODES

What is

semiconductor? It is …………………………………………………………………………….................................

…………………………………………............................................................................................

What is the

“doping”

process?

What is

semiconductors

diodes?

……………………………………………………………………………………………………………

…………………………………………………………………………………………………………

1. Fill in the blank for the statement below.

(a) n-type semiconductor

Silicon like Silicon doped with ………………atoms such as …………… or phosphorus. The

phosphorus atoms have …….. valence electrons. The fifth electron is free to move through

the silicon. The silicon has ….………………….. as majority charge-carriers and it thus

known as an n-type semiconductor.

(b) p-type semiconductors

Semiconductor like Silicon doped with ……………….. atoms such as ………… or indium

has more positive holes. The Boron atoms have only …………. valence electrons with

missing an electron. The majority charge-carriers in this semiconductor are the

……..................... and this semiconductor known as a p-type semiconductor.


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4-5

What is the

function of

diodes?

Semiconductor Diode

A diode is a component (device) that allows _______________to flow in ________ direction only.

A diode acts like a one-way valve to electric current.

The following figure shows structure and the symbol of a semiconductor diode :

Draw the symbol for a semiconductor diode.

How does the p-n junction diode work?

Any further movement of _____________ across the boundary in the depletion layer will be repelled

by the charges in the layer.

The layer of the negative charge in the p-type region will prevent the majority charge carriers from the

__________ region(the electrons) from crossing the boundary. Similarly , the positive charge layer inthe n-type region will prevent the majority charge carriers from the __________ region(the holes) from

crossing the boundary in the opposite direction.

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