Question

Please help me answer these few questions, thank you

a) How to design the voltmeter and ammeter, and how are they connected with the circuits for application?

b) Using the concept of energy band to describe the insulator, semiconductor, and metal, describe the phenomenon of the thermoelectric effect and its application

c) What's the working principle of tape recording and playback in a video tape recorder

d) Describe the working principle of cathode-ray tube used in a traditional television

(GENERAL PHYSICS)

Answer 1

(a) a device named galvanometer is used to design both voltmeter and ammeter

galvanometer as voltmeter

when a large resistance is placed in series with the galvanometer. it behaves as voltmeter

galvanometer as ammeter

when a large resistance is placed in parallel with the galvanometer. it behaves as ammeter

voltmeter is placed in parallel in circuit while ammeter is placed in series. as potential remains same during parallel combination while in series current remains constant.

(b)

valence band and conduction band is overlapped in conductors. while in semiconductors it is very low and in insulators energy gap is high.

thermo electric effect happens when the temperature create potential difference or vice versa.. this effect can be used to generate electricity or to heat objects or cook them

(c)the basic principle of recording is simple. when tape rubs against the recording head, a magnetic field is applied which is directly proportional to the input signal. due to this input signal the magnetic particles are oriented in a specific format which acts as indicators to the pattern of signal stored. When the playback head rubs against the tape, now the signal is reproduced due to the magnetic particles induce similar patterns in the head.

(d)working of cathode ray tube

When a high voltage source is connected to two metal plates, the negatively charged plate is known as cathode emits a beam of electron called as cathode ray. This cathode ray is attracted to the positively charged plate known as anode, where the beam had to pass through a hole and continues travelling to the other end of the tube. When the electron beam hits specially coated surface, a strong fluorescence, or bright light is produced. this moving beam of electrons can behaves like a tiny magnet, and it can also interact with an external magnetic field. due to this external magnetic field the beam of electrons got deflected. In a Televisions’s cathode ray tube, the emitted electrons is focused into a tight beam by a focusing anode and then an accelerating anode accelerate this beam. This tight, high-speed beam of electrons passes through the vacuum and hits the flat screen at the other end of the tube. phosphor coated screen glows when struck by the beam.