Mystery Card
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Approach: One to one Level: Year 4 and year 8
Focus: Exploring closed and open circuits
Resources: Circuit with bulb, battery, mystery card, recording book, pencil
276Kb
Questions/instructions:  

In this activity, you will be using this electric circuit to work out where the electricity goes between the circles on this mystery card.

Give student the circuit. [Click on picture to enlarge.]

First, touch the clips together on the circuit to make sure that the bulb lights up.

Give student mystery card.

Now have a try at touching different circles on the mystery card with the clips to see what happens.

Allow time.

Now touch Circle A with one clip. At the same time, touch Circle B with the other clip.

 
% responses
2007 ('03)
y4
y8
1. What’s happening to the bulb?
    
 
bulb lights up
99 (99)
99 (100)
Now touch A with one clip, at the same time touch C with the other clip.
2. What’s happening to the bulb?
 
bulb doesn’t light up
98 (99)
99 (99)
Now touch A with one clip, at the same time touch D with the other clip.
3. What’s happening to the bulb?
 
bulb lights up
82 (84)
75 (94)
4. Why do you think the bulb didn’t light up when A and C were touched?
Give student recording book and pencil.
Quality of explanation:
(A and C not connected, so circuit not complete, so electricity can’t flow to light up bulb)
clear, detailed explanation
0 (2)
7 (4)
partial explanation
10 (15)
31 (34)
5. Draw what you think is inside the mystery card.
Allow time.
 
A connected to B (directly or via D)
54 (60)
76 (82)
A connected to D (directly or via B)
47 (56)
60 (79)
A not connected to C (directly or indirectly)
81 (88)
86 (88)
6. Use your diagram to explain why the bulb lights up when some circles are touched but not with other circles.
Explanation:
 
clear, convincing explanation, using diagram (explains lighting up AND not lighting up)
5 (7)
17 (24)
partial explanation, using diagram (explains at least one of lighting up OR not lighting up)
21 (25)
38 (38)

Total score:
4–5
5 (11)
28 (34)
3
30 (40)
32 (40)
2
20 (12)
17 (10)
0–1
45 (37)
23 (16)
Subgroup Analysis [Click on charts to enlarge] :
Year 4
Year 8
Commentary:
This task was very popular but there were some problems with the mystery card for year 8 students in 2007 (the A to D link did not reliably produce the intended result). Performance dropped markedly for year 4 students between 2003 and 2007, but similar judgements are not justified for year 8 students because of the equipment problems. Year 4 Pakeha and Mäori students performed similarly.