Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question b - 2021
Question b
Read the following passage and answer the accompanying questions.
December 16, 1947 marked the start of humankind's information age when physicists John Bardeen and... show full transcript
Worked Solution & Example Answer:Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question b - 2021
Step 1
Explain how a photodiode works.
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Answer
A photodiode operates on the principle of reverse bias. When photons are absorbed by the photodiode, they create an electron-hole pair. This absorption leads to a current flow in the reverse direction, resulting in a measurable current output.
Step 2
Diodes can be used to make a bridge rectifier. Draw a circuit diagram of a bridge rectifier.
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Answer
A bridge rectifier consists of four diodes arranged in a diamond shape. The AC input is connected to two opposite corners of the diamond, allowing current to flow through the diodes to produce a unidirectional current output.
Step 3
Sketch the input and output voltage patterns for a bridge rectifier.
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Answer
The input voltage is an alternating current (AC) sine wave, while the output voltage is a direct current (DC) signal. The output voltage waveform resembles a sine wave flipped above the time axis, indicating the rectification process.
Step 4
Draw the structure of a bi-polar transistor.
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Answer
A bi-polar transistor consists of three layers: the collector (n), the base (p), and the emitter (n). The configuration allows for controlled current flow from the collector to the emitter through the base.
Step 5
Draw a circuit diagram of a voltage amplifier. Indicate clearly the input and output voltages.
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Answer
The circuit diagram of a voltage amplifier includes a transistor with the input voltage applied at the base and the output voltage taken across the load resistor connected to the collector.
Step 6
In a voltage amplifier, what is the function of (a) the load resistor, (b) the bias resistor?
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Answer
(a) The load resistor converts changes in collector current to a large output voltage.
(b) The bias resistor ensures that the base-emitter junction is forward biased, enabling the transistor to operate in the active region.
Step 7
A transistor can be used in a circuit to act as a NOT gate. What is the name of this circuit? Draw a truth table for a NOT gate.
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Answer
The circuit is known as a voltage inverter. The truth table for a NOT gate is as follows:
Input
Output
0
1
1
0
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