TRANS MARA DISTRICT PHYSICS PRACTICAL QUESTIONS
1. You are provided with the following:- *
- Dry cell,
- An ammeter (0.25A)
- A voltmeter (0-2.5V)
- A mounted resistance wire,
- 6 connecting wires
- A jockey or a crocodile clip
Proceed as follows:-
(a) Set up the experiment as shown in the figure below:-
(b) With the jockey at X, record the ammeter and voltmeter reading
(c) Vary the length of the mounted wire through which current flows by moving away from X
to a new point Y. record the ammeter and voltmeter readings obtained in the table below.
Length (cm) | 0.0 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 |
Volmetre readings (v) | |||||||||
Ammeter readings (A) |
(d) On the grid provided plot a graph of V (y axis) against I
(e) Determine the slope, M of the graph
(f) The equation of the cell from which current is being drawn is E = V + Ir
Use the equation to determine:-
(i) E.m.f of the cell
(ii) The internal resistance of the cell
2. You are provided with the following:-
- A candle
- a metre rule
- A white screen
- A lens and
a lens holder
- Cross wires mounted on a cardboard
- Plasticine
Procedure:-
(a) Place a metre rule on a bench and hold it in position using plasticine
Arrange the screen, the lens and the cross wires along the metre rule as shown:
(b) Light the candle and place it next to the cross wires such that the flame is at the same level
with cross wires and the cross wires concide with the middle part of the flame.
(c) Adjust the position of the lens so that U=15cm. Now adjust the position of screen until a sharply
focused image of cross wire is obtained in the screen. Record the value of V in the table
(d) Repeat the procedure in (c) above for values of U shown in the table
U(cm) | V(cm) | (U + V)cm |
15 | ||
17 | ||
19 | ||
21 | ||
23 | ||
25 | ||
27 | ||
29 |
(e) Plot a graph of (U + V) against V
(f) From the graph determine the values of V and (U+V) for which the graph has minimum values
V minimum Vm = ___________cm
(U+V) minimum (U + V)m= __________cm
(g) Calculate the values of h1 and h2 from the equations below
(i) h1 = Vm = ________cm
2
h2 = (U+V)m = cm ___________
4
(ii) Determine the average of h1 and h2
h = h1 + h2 = ____cm
2
(h) Using the graph, determine V when U + V = 41.6cm
TRANS MARA DISTRICT PHYSICS PRACTICAL ANSWERS
1. (b) I = 1.00Amps
V = 1.00Volts
(c)
Length L(m) | 00 | 0.1 | 0.2 | 0.3 | 0.4 | 0.5 | 0.6 | 0.7 | 0.8 |
Voltmeter reading V (V) | 1.00 | 1.10 | 1.20 | 1.25 | 1.30 | 1.35 | 1.40 | 1.45 | 1.45 |
Ammeter reading I(A) | 1.00 | 0.80 | 0.60 | 0.50 | 0.40 | 0.35 | 0.30 | 0.25 | 0.20 |
Increasing V 1mk Decreasing 1mk
7-9 correct pairs = 2mks
5-6 correct pairs = 1 ½mks
3-4 correct pairs = 1mk
2 correct pairs = ½ mk
Total = 7mks
(d.) Graph
Labelling – both axes quantity and units shown -1mk
Scale-
Plotting – (½mk each maximum) – 2mks
Straight line – through 3 correctly plotted points– 1mk
Total 5mks
(e) Gradient V = 1.3 – 1.2 = 0.1 = ½ = 0.5
I 0.6 – 0.4 0.2
Gradient = 0.5
(f) (i) V = Ir + E
when I = 0, V = E , y intercept
E = 1.48 ± 0.1Volts
(ii) Gradient S = -r
r = -S
= (0.5) = 0.5
2. (d)
Ucm | Vcm | U +V)cm |
15 17 19 21 23 25 27 29 | 30.5 24.0 21.0 19.0 17.6 16.6 15.8 15.3 | 45.5 41.3 40.0 40.0 40.6 41.6 42.8 44.3 |
(e) On the graph paper – Labelling both axes – 1mk – scale – 1mk
– Plotting (½mk each) max – 2mks Curve – 1mk
(f) Vm = 20cm
(U + V)m = 39.9
(g) (i) h1 = Vm = 20 = 10cm ± 0.2cm
2 2
h2 = (U + V)m = 39.9
4 4
= 9.975cm ± 0.2
(ii) h = h1
+ h2 = 10 + 9.975 = 9.986cm ± 0.2
2 2
(h) Value V when U + V = 41.6
V1 = 16.5cm ± 0.2
V2 = 24.5cm ± 0.2
