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A pupil carried out an investigation into the effect of a diode on d.c - Junior Cycle Science - Question h - 2006
Question h
A pupil carried out an investigation into the effect of a diode on d.c. and on a.c. circuits using an LED. The following circuits were initially set up. What is obs... show full transcript
Worked Solution & Example Answer:A pupil carried out an investigation into the effect of a diode on d.c - Junior Cycle Science - Question h - 2006
Step 1
Circuit A
Answer
In circuit A, the LED glows. This is because the diode allows current to flow in one direction, with the battery providing a direct current (d.c.) supply. The LED requires a certain voltage to glow, and since the battery provides sufficient forward bias, the LED lights up.
Step 2
Step 3
Explanation
Answer
When the batteries were replaced with 6 V a.c. supplies, the LEDs glowed dimly in both circuits. This occurs because the alternating current changes direction constantly. Although the diodes allow current to pass in one direction, they only conduct during half of the cycle (when forward biased). Consequently, the LEDs glow dimly as they only pass current for half the time, resulting in reduced brightness. The diodes in both circuits are forward biased for only about half of the total time the current is flowing.