Page 65 - CT&AI_CLasa_7_Part_1
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Why does the lamp fail to glow? the spring and the battery, the light goes out.
(Abstract Thinking) This is most similar to which problem?
(a) The lamp failed to glow because (Pattern Recognition)
the switch was faulty. (a) A broken filament in the bulb
(b) Rubber is an insulator and it (b) Using a battery with the wrong
prevents current from flowing voltage
between the wire and the terminal.
(c) Having insulation (non-conductor)
(c) Insulation does not affect current blocking the path
flow and the problem must be a
(d) The switch being clicked too hard
dead battery.
7. Tanya connects two cells in series to power an
(d) The bulb needs more voltage to LED. She closes the switch but the LED does
start glowing. not glow. The LED's shorter wire (negative
5. The '+' and '−' markings on a battery have terminal) connects to the positive end of the
been scratched off and are unreadable. battery and the longer wire (positive terminal)
Meena must identify which terminal is connects to the negative end.
positive and which is negative. She has: one Why does the LED not glow, and which wires
LED (with clearly visible longer and shorter must be swapped to fix it?
wires), connecting wires, and a small bulb. (Algorithmic Thinking)
Design the simplest method using an LED to (a) The LED needs three cells — two are
identify the battery terminals, and explain the insufficient.
logic behind it. (Algorithmic Thinking)
(b) The LED is connected with reversed
(a) Hold the LED close to the battery
terminals. Check which side polarity; swap the two LED wires so
appears brighter. Use this to decide the longer wire (+) connects to the
the positive terminal. battery's positive end and shorter
wire (−) to the negative end.
(b) Connect the LED; if it glows, the
(c) The cells are in the wrong order —
terminal joined to the longer
positive of cell 1 should connect to
wire is positive; if not, reverse the
positive of cell 2.
connections.
(d) The LED is broken — LEDs in series
(c) Touch both terminals together —
sparks will come from the positive with two cells always burn out.
side. 8. You have six cells (A–F), some are working,
some are dead and only one bulb, one switch,
(d) Use a magnet to detect which and connecting wires. You must test all the six
terminal is positive. cells to find which works, using the minimum
6. In a flashlight, the spring at the bottom must number of steps. A classmate suggests testing
touch the shiny metal part of the battery. If a two cells at a time in series to save time.
piece of paper falls inside and sits between
Electricity: Circuits and their Components 63
