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Phy302:Alternating Circuit Theory Question Paper

Phy302:Alternating Circuit Theory

Course:Computer Science

Institution: Kenya Methodist University question papers

Exam Year:2013

END OF 1ST TRIMESTER 2013 (SCHOOL BASED) EXAMINATION

FACULTY : EDUCATION AND SOCIAL SCIENCES
DEPARTMENT : EDUCATION
UNIT CODE : PHY 302
UNIT TITLE : ALTERNATING CIRCUIT THEORY (AC THEORY)
TIME : 2 HOURS

INSTRUCTIONS: answer any three questions

Question One

A series RLC circuit with L = 160mH, C= 100 F, and R = 40.0 is connected to a sinusoidal voltage V(t) = (40V) sin t, with = 200 rad/s

What is the impedance of the circuit? (10 Marks)

Let the current at any instant in the circuit be I(t) = Io sin ( t - ). Find Io (5 Marks)

What is the phase ø? (5 Marks)

Question Two

Define resonant frequency (2 Marks)

A sinusoidal voltage V(t) = 200V sin t is applied to a series RLC circuit with L =10.0mH, C = 100nF and R = 20.00?. find the following quantities
The resonant frequency (5 Marks)
The amplitude of the current at resonance. (3 Marks)
The quality factor Q of the circuit. (5 Marks)
The amplitude of the voltage across the inductor at the resonant frequency (5 Marks)
Question Three

The circuit below shows an RL filter

Let the inductance be L = 400mH and the input V1n = (20V) sin t,
where = 200 rad/s
What is the value of R such that the output voltage lags behind the input voltage by 30o (8 Marks)
Find the ration of the amplitude of the output and the input voltages (5 Marks)
What type of filter is this circuit, high pass or low pass give reason. (2 Marks)
If the positions of the resistor and the inductor are switched, would the circuit be a high pass or low pass. Give a reason. (5 Marks)

Question Four

What are the advantages of AC over DC. State and explain three advantages. (6 Marks)

Explain three ways by which power is lost in transformer. (6 Marks)

How are the three ways above in 4 (b) minimized (3 Marks)

How does a transformer achieve impedance matching? (5 Marks)

Question Five

Define a phasor diagram. (2 Marks)

Explain how full wave and half wave rectification is achieved. (8 Marks)

Transform the following sinusoids to phasors
i = 6cos (50t – 40o)A (2 Marks)
V = -4 sin (30t + 50o)V (2 Marks)

Explain how ac is generated in an alternator. (use diagrams) (6 Marks)

Phy302:Alternating Circuit Theory Question Paper

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