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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 Eo of the voltmeter
Eo= …………………………………………………………………………….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
Voltage (V) Volts | 0.5 | 1.0 | 1.5 | 2.0 | 2.5 | 2.7 |
Current (I) A | ||||||
I (A-1) I | ||||||
R = V (Ohms) I |
(e) Plot a graph of 1/I (y-axis ) against R
(f) Determine the slope S of the graph
(g) (i) Find Ro, the value of R when1/I = 0 A-1
(ii) Evaluate 1/S – Eo
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:-
- 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:
Object distance, Ucm | 3.0 | 4.0 | 6.0 | 7.0 | 8.0 | 10.0 | 11.0 | 12.0 |
Image distance , Vcm | ||||||||
M = V U |
(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) Eo = 3.2 0.1 volts
Voltage (V) Volts | 0.5 | 1.0 | 1.5 | 2.0 | 2.5 |
|
Current (I) A | 0.67 | 0.48 | 0.36 | 0.24 | 0.12 | 0.06 ± 0.02 |
1 (A-1) I | Candidate’s values correct to 3d.p | |||||
R = V (Ohms) I |
|
(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 = Ro = 5Ω ±1 *KSM*
I
(ii) 1 – Eo
S
= 1 – 3.2
0.3
= 0.1± 0.01 V
Question 2
(a) f = 20 1cm
(c) (i) erect (ii) virtual (iii) magnified
Object Distance, Ucm | 3.0 | 4.0 | 6.0 | 7.0 | 8.0 | 10.0 | 11.0 | 12.0 |
Image distance , Vcm | 3.0 | 5.0 | 7.8 | 10.0 | 13.3 | 18.5 | 22.0 | 29.1 ± 0.2 |
M = V U |
|
(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