Text 20
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Electrical measuring units and instruments
Any instrument which measures electrical values is called a meter .An ammeter measures the current in amperes. The unit is named after Andre Marie Ampere a French scientist, who discovered a great number of facts about electricity over a hundred years ago. The abbreviation for the ampere is amp. A voltmeter measures the voltage and the potential difference in volts. The volt is named alter Alessandro Volta, an Italian scientist.
The
current in a conductor is determined by two things, the voltage
across the conductor and the resistance of the conductor. Every
material object offers some resistance to the flow of an electron
current through it. Good conductors like the metals, copper, silver
and aluminium offer very little resistance, while nonconductors
such
as glass, wood and paper offer a very high resistance. The unit by
which resistance is measured is called the ohm.
The resistance in practice is measured with the ohmmeter. A wattmeter
measures electrical power in watts.
Answer the questions:
What is called a meter?
What does an ammeter measure?
What is the current determined by?
What can you say about non conductors?
Для спеціальності квп text 16
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Preferred value resistance box
This Resistance Box consists of four separate switches which will select resistances in the 10% preferred value range. Dial 1 resistors from 100 ohms to 820 ohms. Dial 2 resistors from 1 Kohm to 8.2 Kohms. Dial 3 resistors from 10 Kohms. Dial 4 resistors from 100 ohms to 820 Kohms.
The individual resistors are high stability carbon types with an accuracy of ± 1%.
Each dial is individually connected and screened from the other three dials in the box so that separate dials can be used in different boxes of the same circuit without interconnection. Connection is by co-axial plugs. The whole is contained in a metal case.
Rating: 1 watt.
Answer the questions:
What does the Resistance Box consist of?
What are the individual resistors?
How is each dial connected and screened?
Text 17
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Dual transistor power supply type 423
The Type 423 Power Supply is manufactured on an open chassis and is intended to be incorporated into professional equipment but it can equally well be used on the laboratory bench.
The unit provides two completely independent and isolated supplies and the output can easily be adjusted by the purchaser. The voltages provided cover those commonly used by transistor circuit designers.
Specification
(the following specification applies to both supplies)
Output Voltages: 10-12v,15-18v, and 24v.
Output Current: 0-1Amp.
Ripple and noise:(at 1 Amp) Less than 5 mV pk.
Supply Voltage: 100/220 v
Dimensions:
Height 5.0 ins.(12.70 cms)
Width 6.0 ins. (15.24 cms)
Weight 8.0 lbs.(3.6 kg)
Answer the questions:
How can the Type 423 Power Supply be used?
What does the unit provide?
What is the voltage supplied?
What are the dimensions?