Question

Basic Electronics

In a classical model of the Hydrogen atom, the electron is moving around the proton on a circular orbit with radius r. Assume that a uniform external electric field is applied so that the orbit of the electron is displaced by a small, compared to the radius of the orbit, distance Ax perpendicular to the plane of the orbit, and assume that the radius of the orbit remains unchanged.

E \approx \frac{e}{4 \pi \epsilon_{0} r^{3}} \Delta x

(a) Show that the electric field strength required to maintain the displacement of the orbit is given approximately by the expression below, where e is the magnitude of the charge of the electron:

(b) Assume that in hydrogen gas (H2) each atom in a molecule does not interact with the other atom in the same molecule, or with any other atoms in neighbouring molecules.Assume that when a uniform external electric field is applied to the gas, all atoms are oriented such that the plane of the electron orbit is perpendicular to the field. Assume that the hydrogen gas is a dielectric, and that its polarisation is proportional to the magnitude of the external field. Under these assumptions, and using the result in part(a) above, show that the electric susceptibility Xe of the hydrogen gas H2 with a number of N/V molecules per unit volume, is given by:

\chi_{e} \approx 8 \pi \frac{N}{V} r^{3}

(c) Calculate, using the result in part (b) above, the electric susceptibility of hydrogen gas at a pressure of 105 Nm2 and a temperature of 293 K. Assume that hydrogen behaves as an ideal gas, which allows you to use the ideal gas equation. Use the Van de Waal's radius of the hydrogen atom, 120x10-12 m.  Verified     ### Question 44843  Basic Electronics

4a. Based on Fig. 4a, explain the fundamental working principle of a PN LED.
b. Fig. 4b shows phosphorus and boron doping of silicon. Using the diagram,explain how doping is achieved, the type of doping and the role of electrons and holes in the resultant material.
c. State the Stefan-Boltzmann law, explain its parameters and how it could be used as a basis for a passive infra-red (PIR) thermal imaging system.

### Question 44842  Basic Electronics

OExplain what is the main focus of the branch of science known as"Metrology' and how it may be related to sensors.
(b) The terms accuracy, precision, resolution and linearity are clearly defined in Metrology. Explain these terms, giving examples or-sketching diagrams to highlight key features.

### Question 44841  Basic Electronics

(a) Explain what is a low pass filter. Sketch a circuit diagram of apassive low pass filter and its bode plot for gain and phase. Explainthe significance of the -3dB point and what would the roll-off rate befor a 3rd-order low pass filter.
(b) Contrast the low pass filter with a high-pass filter. Sketch a circuit diagram of a passive high pass filter and its bode plot for gain and phase.[10 Markel
(c) What is the main difference between an active and a passive filter and contrast at least one key feature of an analogue Bessel filter versus an analogue Butterworth filter.

### Question 44840  Basic Electronics

1.(a) Many sensors have a number of key characteristics in common,such as sensitivity and stability. List a further set of 5 key characteristics and explain why they are important.
(b) Explain what type of sensor is a silicon photodiode and its operation.What are the two main configurations of a photodiode and which of these is useful if the response of the photodiode needs to be relatively fast compared to a conventional photodiode.40 Modike)

### Question 44748  Basic Electronics

The partial ac equivalent circuit of an amplifier is shown below. If R1 = 38 kohms and R2 = 1.99 kohms, find the overall voltage gain Vo/Vg (approximately)?

### Question 44747  Basic Electronics

Which of the following is the best estimate for the resistance seen by the source, Rin, and the outpu tresistance seen by the load, Ro, for the circuit shownbelow?
O 10 x R1, 1 m2
O R1, 1N
O 10 x R2, 100 ohms
R2, 4.7 kohms

### Question 44746  Basic Electronics

The amplifier shown below is very close to being an ideal trans resistance amplifier with a gain of 4.7 kohms.If Rg is 1.6 k2 and RL is 2.0 kohms, calculate the overall gain Vo/Vg.

### Question 44745  Basic Electronics

The open loop gain, Aol of an amplifier with a feedback fraction of B =0.53, changes from 100 to110 because of temperature changes (hint: a large change!). Calculate the percentage change in the closed loop gain, Af. (Don't put the % sign in the answer).Type your answer...

### Question 44744  Basic Electronics

The Transr esistance gain of an amplifier is defined as the ratio of
O The input voltage to the output current
The output current to the input voltage
O The output voltage to the input voltage
O The feedback current to the output voltage
O The output voltage to the input current

### Question 44743  Basic Electronics

Estimate the magnitude of the loop gain of the circuit shown below. The op-amp has the following parameters: differential input resistance, rd = 1 MQ,output resistance, ro = 100 ohms open-loop gain, Aol-105 assume R1= 98.30 k ohms and R2 6.90 k ohms

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