4. ELECTRONICS [……/25 x 100 = ………% ]Instruction: Answer all questions in this section.
4.1 Understanding the uses of the Cathode Ray Oscilloscope (C.R.O)
A student is able to :
explain thermionic emission. Describe the properties of cathode rays. Describe the uses of a cathode ray oscilloscope.
-- Measure potential difference using the C.R.O. -- Measure short time intervals using the C.R.O. -- Display wave forms using the C.R.O. Solve problems based on the C.R.O. display
1. ______________________ is the process where by ____________ are released from the surface of a heated metal.
2. The properties of cathode rays
(i) They travel in ________________ lines.(ii) They are fast moving ____________ and therefore can generate ________when
they hit the fluorescent screen.(iii) They are deflected by _________ and ____________ fields and are _________
charged.
3. The diagram shows the structure of a simple cathode ray tube.
(a) Name the components labeled P, Q, R, S and T.
Component Name of the component Function of the componentPQRST
Name:……………………………………………………. Electronics/Form 5 i. display _________________ ii. measure ________________ of DC and AC supply iii. measure a _________________________
4. The figure below shows a trace formed on the screen of a CRO.
If the Y-gain control on the CRO is set at 0.5 V cm-1 and the time-base is set at 5 ms cm-1.
Find the peak voltage VP , Period, T and Frequency, f.
peak voltage VP Period, T Frequency, f.
Peak voltage, VP = =
Period, T = =
frequency, f = 1/T = =
5. If the same signal is applied to the CRO but the time base is readjusted to 10 ms/cm, draw a sketch to show the trace that will now be formed on the screen?
Name:……………………………………………………. Electronics/Form 5A student is able to :
Describe semiconductors in terms of resistance and free electrons Describe n-type and p-type semiconductors. Describe semiconductor diodes and their function. Describe the use of diodes as rectifiers. Describe the use of a capacitor to smooth the output current and output voltage from a
rectifier circuit.
1. (a) A semiconductor is a material whose resistance is between the resistance of a _______________ and an ____________________ .
(b) ___________ is a process when small amounts of ________________ are added to pure semiconductors causing an increase in the _________________ of the material.
(c) A p-type semiconductor is produced when a semiconductor material such _________________ is doped with a ____________ element like _________________
(d) A n-type semiconductor is produced when a semiconductor material such as germanium/silicon is doped with a ____________________ element like _____________________ .
. (e) A ______________________ is a p-n junction diode where the p-type material is called the __________ and the n-type material is called the ______________
(f) In ___________-biased a current ________ through the diode but in _________-biased current ________________ through the diode.
(g) _____________-biased, Bulb lights / does not light up
_______ _______ Symbol of diode
2. Diagram 1 shows an electric circuit with one diode and the trace produced is shown on a CRO connected across the resistor R.Diagram 2 shows an electric circuit with four diodes and the trace produced is shown on a
A student is able to: Describe a transistor in terms of its terminals. Describe how a transistor can be used as a current amplifier. Describe how a transistor can be used as an automatic switch.
1. Name the two types of transistors as shown in Figure 4.31(a) and 4.31(b) and label the three terminals
___________ _______
__________
Figure 4.31 (a) Type of transistor : _______ transistor
Figure 4.31 (b) Type of transistor : ________ transistor
2. Transistor as a Current Amplfier
A transistor can function as a ______________________ by allowing a small
current to control a larger current. Rheostat R changes the _______ current. A
_________ change in the base current, IB will cause a _______ change in the
collector current, IC. The current amplification can be calculated as follows:
As VS ____________, the base current ______________ causing the collector current to _______________ by a large magnitude. This will cause the relay to ___________ the circuit and switch on the motor.
A student is able to: Draw symbols for the following logic gates .
i. ANDii. ORiii. N0Tiv. NANDv. NOR
Build truth tables for logic gates in combination for a maximum of 2 inputs. State that logic gates are switching circuits in computers and other electronic systems. Describe applications of logic gates control systems.
1. Draw symbols for the following logic gates and state their action in a truth table
i. AND ii. OR
iii. N0T iv. NAND
v. NOR
2. The figure below shows a circuit consisting of three different logic gates.
(b) Complete the truth table for the system shown above.
Input OutputA B0 00 11 01 1
(c) (i) The combination of the logic gates above can be replaced by a single logic gate. What is this equivalent logic gate?
(ii) Give the Boolean equation for the logic gate in your answer in ( c)(i) above.
2. The circuit below shows a logic circuit used in a cold room where frozen meat is stored. The alarm will be turned on if the temperature of the cold room is too high. The buzzer will be turned OFF if the output logic is 0 and be turned ON if the output logic is 1.
(a) Name the logic gate used in the circuit above.
