Anglicky v odborných p?edm?tech "Support of teaching technical subjects in English 

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Anglicky v odborných předmětech &quot;Support of teaching technical subjects in English “. Tutorial : Mechanic - electrician Topic : Basics of electrical engineering the 2nd. y ear M easuring the capacity Prepared by: Ing. Jiří Smílek.

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Anglicky v odborných předmětech"Support ofteachingtechnicalsubjects in English“

Tutorial: Mechanic - electrician

Topic: Basicsofelectricalengineering

the 2nd. year

Measuringthecapacity

Prepared by: Ing. Jiří Smílek

Projekt Anglicky v odborných předmětech, CZ.1.07/1.3.09/04.0002

je spolufinancován Evropským sociálním fondem a státním rozpočtem České republiky.

Measuring capacity
• The basic unit- 1 F (farad)
• 1 farad is the capacity of an electric capacitor, which has a voltage of 1V and holds a charge of 1C.
• Capacitance is:
• Directly proportional to:
• the active area S
• permittivityε
• Inversely proportional to:
• the distance between the plates d
• C= ε S/d
• Definition of units of capacity
Measuring capacity
• Volt-ampere (Ohm’s) method – applied to the measurements of large impedances
• Supply voltage must have a known and constant frequency
• Involvement of a small C
• Involvement of a large C
• The used method:
Measuring inductance
• Calculation 1 – when an AC current:
• We must know:
• current
• voltage
• When we don’t know the value of the capacity CX we calculate it from basic data from an A-metre and a V-metre
• Capacitive reactance
• Of which we don’t know the capacity, the angular frequency – ω will help
• Or the help of frequencyf
Measuring inductance
• Calculation 2:
• When measuring it is important that there is an AC current flowing through the circuit
• If not, you should make a re-count on a replacement scheme
• Phasor diagram
Measuring capacity
• Measuring capacity distribution of an electric charge
• The used method:
• The measurement procedure:
• The capacity of the capacitor C is known and the position I of switch p is charged with a voltage U and a charge Q.
• Switch the switch to position 2;
• by an unknown capacity CX connected in parallel to capacity C.
• The charge is divided into two capacitors and the voltage U is subtracted again from the voltmeter.
• For the switch applies
• In position 1 - Q = U.C
• In position 2 - Q = U.Cx + UxCx.
• Unknown capacity of a capacitor

Activities for students – questions

• Describe how to define a unit of capacity
• Name for what is the proportional capacity of the capacitor
• Write what are the requirements for power voltage
• Draw a circuit for measuring
• small C
• large C
Activities for students – questions
• Calculate an example:
• A block capacitor has an unreadable data capacity; we can find out about the circuit with an ammeter. The ammeter showed a currentI = 2.76A at a voltage of 230V, 50 Hz
• Capacitive reactance
• XC =
• Capacitance
• CX=
Bibliography
• Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7.
• Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013.