Anglicky v odborných předmětech "Support of teaching technical subjects in English “

1. 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.

2. 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

3. 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:

4. 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

5. 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

6. 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

7. 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

8. 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=

9. Bibliography • Mužík, J. Management ve vzdělávání dospělých. Praha: EUROLEX BOHEMIA, 2000. ISBN 80-7361-269-7. • Operační program Vzdělávání pro konkurenceschopnost, ESF 2007 – 2013. • Dostupné na: http://www.msmt.cz/eu/provadeci-dokument-k-op-vzdelavani-pro-konkurenceschopnost • Učebnice Elektrická měření – Ing. Pavel Vylegala, SŠE Ostrava, 2006 • Učebnice Elektrické měření – SNTL, 1981 • Elektrotechnika - Laboratorní cvičení pro bakalářské studium - Doc. Ing. Miloš Hammer, CSc.