# 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**

- State the maximum power transfer theorem

- 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

- What is the efficiency of the circuit at the maximum power transfer condition?
- 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) | 20.20 | 22.80 | 26.95 | 30.95 | 32.20 | 36.30 | 38.70 | 43.40 | 45.20 |

R(kohms) | 11.90 | 10.80 | 9.17 | 7.87 | 7.50 | 6.43 | 5.89 | 4.99 | 4.69 |

Table 1

- Plot the graph of 1/T ( ̊C
^{-1}) against log R

- Find the slope of the graph

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

- Name 4 apparatus needed for this experiment.

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

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

**QUESTION THREE**

- Distinguish between an active and a passive network
- 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.

- 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**

- State the reciprocity theorem.
- State 2 precautions you must ensure while carrying out this reciprocity experiment.

- The formula for electrical current per ohms law is?

- A path between two or more points along which an electrical current can be carried is called a ____________
- 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**

- Describe how an Op-amp may be used as :
- Voltage to current converter.
- Current to voltage converter.

- an integrator.

- 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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