# PHY320 : PHYSICS LABOURATORY (2014)

NATIONAL OPEN UNIVERSITY OF NIGERIA

14/16 AHMADU BELLO WAY, VICTORIA ISLAND, LAGOS

SCHOOL OF SCIENCE AND TECHNOLOGY

MARCH/APRIL 2014 EXAMINATION

COURSE CODE: PHY320

COURSE TITLE: PHYSICS LABOURATORY

TIME ALLOWED: 2HOURS

INSTRUCTION: ANSWER QUESTION ANY FOUR QUESTIONS

QUESTION ONE

1. State the maximum power transfer theorem

1. Plot a graph between load resistance RL against the power transferred, for several values between 1  kΩ  , 5 kΩ,10 kΩ,15 kΩ 20  kΩ for the circuit Fig 1 :

Fig 1

1. What is the efficiency of the circuit at the maximum power transfer condition?
2. State the precautions needed to verify this theorem.

QUESTION TWO

In an experiment involving A NTC thermistor, the table 1 below was obtained;

 Temp (C) 20.2 22.8 26.95 30.95 32.2 36.3 38.7 43.4 45.2 R(kohms) 11.9 10.8 9.17 7.87 7.5 6.43 5.89 4.99 4.69

Table 1

1. Plot the graph of 1/T ( ̊C-1) against log R

1. Find the slope of the graph

• State 2 precautions you must ensure while carrying out this experiment.

1. Name 4 apparatus needed for this experiment.

1. List a few metals, semiconductors, and insulators that you are familiar with.

1. Distinguish between metals, semiconductors and insulators in terms of energy gap.

QUESTION THREE

1. Distinguish between an active and a passive network
2. With a suitable ray diagram, explain the principle of Young’s double slit experiment.
• State two precautions you would take to ensure accurate results in Young’s double-slit experiment.
1. A double-slit source with slit separation 0.2 mm is located 1.2 m from a screen. The distance between successive bright fringes on the screen is measured to be 3.30 mm. What is the wavelength

of the light?

QUESTION FOUR

1. State the reciprocity theorem.
2. State 2 precautions you must ensure while carrying out this reciprocity experiment.
• The formula for electrical current per ohms law is?
1. A path between two or more points along which an electrical current can be carried is called a ____________
2. Electric current is the flow of _______ from a ______ polarity to a _________ polarity.

In a simple DC circuit with a constant voltage, where the resistance increases current will ______________

QUESTION FIVE

1. Describe how an Op-amp may be used as :
2. Voltage to current converter.
3. Current to voltage converter.
• an integrator.
1. a differentiator.

(b)

(i) Outline the principle of the measurement of magnetic flux density using the op-amp.

(ii) State the precautions you would take in an experiment to measure electric charge using an op amp.

QUESTION SIX

(a)

(i) Distinguish between a positive and negative lens.

(ii) With suitable ray diagrams, explain the terms focus and focal length of a converging and diverging lens.

(b)

(i) In an experiment to determine the focal length of a converging lens,    was plotted on the horizontal axis and    on the vertical axis (u and v are the object and image distances respectively). Explain, with suitable equations, how you would use this graph to obtain the power, focal length and linear magnification of the lens.

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