KISUMU WEST DISTRICT PHYSICS PRACTICAL QUESTIONS AND ANSWERS

KISUMU WEST DISTRICT PHYSICS PRACTICAL QUESTIONS

Question 1

• You are provided with the following:-
  
• A voltmeter
  
• An ammeter
  
• Two dry cells and a cell-holder
  
• A switch
  
• A potentiometer or Rheostat
  
• Six connecting wires

Proceed as follows:-

(a) Set-up the circuit as shown in figure 1 below:-

fig. 1

(b) With the switch open, record the reading E_o of the voltmeter

E_o= …………………………………………………………………………….volts

(c) Close the switch. Adjust the voltmeter to read 0.5volts using the potentiometer or Rheostat.

Measure the corresponding current with the ammeter and record in table 1

(d) Repeat the procedure in (c) using different voltmeter readings provided in tale 1 below, each

time recording the corresponding ammeter reading. Complete the table

 Table 1

 (e) Plot a graph of ¹/_I (y-axis ) against R

 (f) Determine the slope S of the graph

 (g) (i) Find R_o, the value of R when¹/_I = 0 A^-1

(ii) Evaluate ¹/_S – E_o

Question 2.

You are provided with the following apparatus:

• A thin lens marked L
  
• A lens holder
  
• An office pin
  
• An optical pin
  
• A white screen
  
• A metre rule
  
• Some plasticine

Proceed as follows:-

1. Set-up the apparatus as in figure 3 below

Focus a distant object, say a window, by letting the lens L position invariant. Meanwhile slide the

white screen back and forth till a sharp image of the distant object; window, appears clearly on the

white screen.

Measure the distance, f, between the lens L and the white screen

f = ………………………….cm

(b) Set-up the apparatus as shown in figure 4 below. Use the office pin as an object and place it

at a distance less than f; of the lens L.

Mount the office pin on plasticine to enhance its proper visibility through the lens L

Take the optical pin and use it as a search pin. Find a position of no parallax between the search

pin and the image through the lens L. Measure the distance

between the office pin and the image, V in centimeters

(c) Describe the image characteristics

(d) Put the object pin near the lens L, that is, at u = 3cm. Observe through the lens L such that

there is no –parallax between the object and the image, i.e. when V= 3cm

(e) Repeat the procedure using at least six different values of u. complete table 2 below:-

Table 2:

(f) Plot a graph of U (y-axis) against V

(g) (i) from your graph, find the value of V when u  f

(ii) State the application of this practical in real life experience

KISUMU DISTRICT PHYSICS PRACTICAL ANSWERS

 Question 1.

 (b) E_o = 3.2  0.1 volts

 (e) graph

 (f) Slope = 3.0 – 1.50

5.0 – 0

 = 1.5

5.0

 = 0.3 A-¹^-1

 (g) (i) When 1 = 0 , r = R_o = 5Ω ±1 *KSM*

I

 (ii) 1 – E_o

_S

 = 1 – 3.2

0.3

 = 0.1± 0.01 V

Question 2

(a) f = 20 1cm

(c) (i) erect (ii) virtual (iii) magnified

(f) graph …

(g) (i) when u  f, V = Infinitely large number (undefined)

N/B: i.e when object is at F, the image is formed at infinity

(ii) Application: Magnifying lens