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    Is testing cells two-at-a-time in series a risky    10.  A solar panel is used to power a toy fan. On a
                         strategy.                  (Decomposition)           sunny day the fan spins fast. On a cloudy day
                                                                              the fan barely moves. At night the fan stops
                                (a)   Testing two at a time is fine — if the
                                                                              completely. A student claims, 'The solar panel
                                   bulb glows, both cells are working.
                                                                              is a battery, it stores energy in the day and
                                (b)   Testing two in a series is risky — if   releases it at night.'
                                   the bulb does not glow, you cannot
                                   tell which of the two cells is dead.

                                (c)   Testing two at a time is better —

                                   if both are dead the bulb glows
                                   brighter.

                                (d)   Series testing works for dead cells
                                   but not for working cells.                 Is the student's claim correct?
                                                                                                      (Abstract Thinking)
                      9.  A circuit has a battery, wires, and an LED. The
                         connections are proper, but the LED still does             (a)   Correct — solar panels store energy
                         not glow. Which is the most logical reason?                   like a battery and release it at night.
                                                  (Abstract Thinking)               (b)   Incorrect — a solar panel converts
                                (a)   LED is connected in reverse                      light  energy  into  electrical energy
                                   direction.                                          only while light  falls  on it and it
                                                                                       does not store energy.
                                (b)   LED has no resistance.
                                                                                    (c)   Correct  — both  solar  panels and
                                (c)  LED always need two batteries.
                                                                                       cells store chemical energy.
                                (d)   LED only works in sunlight.
                                                                                    (d)   Incorrect — both  solar  panel and
                                                                                       cell provide electricity only at night.

                                       Two lamps L  and L  are connected in series with a battery. The filament of L  is
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                                       broken. Rajan says: 'L  will still glow because it has its own filament.' Priya says:
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                                       'Neither lamp will glow.' The switch is closed.
                                       Who is correct, and what is the scientific reason?
                                             (a)  Rajan — L  has its own filament so it glows independently.
                                                           2

                                             (b)   Priya — a broken filament in L  breaks the circuit; no current flows so
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                                                 neither lamp glows.
                                             (c)   Both glow dimly — current finds an alternative path around the broken
                                                 filament.

                                             (d)   Only L  glows — current stops at the broken filament and heats L  instead.
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                     64        Computational Thinking-7 (Science)

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