* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

# Download Module Title: Electrical Science 2 - CIT

Survey

Document related concepts

Opto-isolator wikipedia, lookup

Crystal radio wikipedia, lookup

Negative resistance wikipedia, lookup

Electrical engineering wikipedia, lookup

Galvanometer wikipedia, lookup

Resistive opto-isolator wikipedia, lookup

Switched-mode power supply wikipedia, lookup

Valve RF amplifier wikipedia, lookup

Flexible electronics wikipedia, lookup

Power MOSFET wikipedia, lookup

Regenerative circuit wikipedia, lookup

Integrated circuit wikipedia, lookup

Two-port network wikipedia, lookup

Current source wikipedia, lookup

Zobel network wikipedia, lookup

Electronic engineering wikipedia, lookup

Lumped element model wikipedia, lookup

Electrical ballast wikipedia, lookup

Index of electronics articles wikipedia, lookup

Transcript

CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ Autumn Examinations 2009 Module Title: Electrical Science 2 Module Code: ELEC6019 School: Electrical and Electronic Engineering Programme Title: Bachelor of Engineering in Electrical Engineering – Stage 1 Programme Code: EELEC_7_Y1 External Examiner(s): Internal Examiner(s): Mr. Gerard Beecher and Dr. Maeve Duffy Mr. Noel Mulcahy Instructions: Answer All Questions Duration: 2 Hours Sitting: Autumn 2009 Requirements for this examination: Use of a Scientifc Calculator is permitted. Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator. Page 1 of 3 Q1. a. A circuit, having a resistance of 4Ω, an inductance of 0.5H and a variable capacitance in series, is connected across a 100V, 50Hz supply and a current is drawn. Calculate: i) the value of capacitance to give resonance; (8 marks) ii) the voltages across the inductance and the capacitance; (6 marks) iii) the Q factor of the circuit. (2 marks) b. A similar circuit consists of a 115Ω resistor, a 422mH inductor and a 24µF capacitor connected in series across a 230 V, supply. Determine the resonant frequency of this circuit. (4 marks) Q2. a. A circuit contains three branches, a resistance of 23Ω, an inductor of 0.08H and a 36µF capacitor across a 230 V, 50Hz supply. Determine i) the current taken by the circuit; (6 marks) ii) the phase angle of the circuit; (3 marks) iii) the power factor of the circuit; (2 marks) iv) the power dissipated in the resistor; (4 marks) b. Draw the phasor diagram to represent the current. (5 marks) Q3. A milli-ammeter requires 100mV across its terminals to give full-scale deflection with a current of 10mA flowing through the coil. a. Calculate the resistance required in series with the meter so that the combination of meter plus resistor would give a full-scale deflection for 50 V. b. c. (8 marks) How could the milli-ammeter be converted to an ammeter with a full-scale deflection 5.0A and what value of resistance would be required? (8 marks) Sketch the circuit in each case above. (4 marks) Q4. a. List the relative advantages and disadvantages of lead-acid and alkaline cells. (6 marks) b. A battery of 50 cells connected in series is charged through a fixed resistor from a constant 120 V supply. At the beginning of the charge, the e.m.f per cell is 1.9 V and the charging current is 4 A. When charging is almost complete, the e.m.f. per cell has risen to 2.2 V. Each cell has an internal resistance of 0.02 Ω. Calculate the value of the external resistor and the current at the end of the charge. (14 marks) Page 2 of 3 Some Useful Formula Q=CxV F=BxIxL E=BxLxv Specific Heat Capacity of Water = 4.184 J/g/°C ∆Q = m x c x ∆T P = I x V, P = I2 x R, P = V2 / R W = ½ x C x V2 XL = 2 x π x f x L XC = 1 2xπ x f xC Z = R 2 + ( X L − X C )2 Series circuits p.f. = R Z Parallel circuits p.f. = IR IT Page 3 of 3