In Pradeep's classroom, the fan was running very slowly. Due to which, his teacher was sweating and was restless and tired.All his classmates wanted to rectify this. They called an electrician who came and changed the capacitor only, after which the fan started running fast.
Answer the following questions based on the above information:
(i) What energy is stored in the capacitor and where?
(ii) A thin metal sheet is placed in the middle of a parallel plate capacitor. What will be the effect on the capacitance?
(iii) What values did the classmates have?

(i) In a meter bridge, the balance point is found to be at 39.5 cm from the end A, if an unknown resistor X is in the left gap and a known resistor Y of resistance 1.25 \(\Omega\) is in the right gap. Determine resistance of X. Why are the connections between resistors in a Wheatstone or meter bridge made of thick copper strips?
(ii) Determine the balance point of the above bridge, if X and Y are interchanged.
(iii) What happens, if the galvanometer and cell are interchanged at the balance point of the bridge? would the galvanometer show any current?

Explain using a labelled diagram, the principle and working of a moving coil galvanometer. What is the function of
(i) uniform radial magnetic field
(ii) soft iron core?
Also, define the terms
(iii) current sensitivity and
(iv) voltage sensitivity of a galvanometer.
Why does increasing the current sensitivity not necessarily increase voltage sensitivity?

In the birthday party of Kamal, his parents gave big slinkies to all his friends as a return gift. The very next day, during the physics class Mr. Mohan, the teacher explained them about the production of magnetic field using current carrying coil and also said that they can make permanent magnet, using such coils by passing high currents through them. That night Priyanshu, a friend of Kamal, asked his father about the coils, and their shape. His father asked him to bring the slinky, that his friend gave and explained the use of toroid and solenoid.
Read the above passage and answer the following questions:
(i) What value did Priyanshu's father have?
(ii) What is the difference between solenoid and toroid?
(iii) Give the value or magnitude of magnetic field in solenoid.

Niyaz was using galvanometer in the practical class. Unfortunately, it fell from his hand and broke. He was upset, some of his friends advised him not to tell the teacher but Niyaz decided to tell his teacher. Teacher listened to him patiently and on knowing that the act was not intentional, but just an accident, did not scold him and used the opportunity to show the internal structure of galvanometer.
(i) What are the values displayed by Niyaz?
(ii) Give the principle of moving coil galvanometer.
(iii) How can you increase the sensitivity of a galvanometer?

(i) A voltage V = V₀ \(sin\ \omega t\) applied  to a series L-C-R circuit derives a current I = I₀ \(sin\ \omega t\) in the circuit. Deduce the expression for the average power dissipated in the circuit.
(ii) For circuits used for transporting electric power, a low power factor implies large power loss in transmission. Explain.
(iii) Define the term wattless current.

Define magnifying power of a telescope. Write its expression. A small telscope has an objective lens of focal length 150cm and an eyepiece of focal length 5cm. If this telescope is used to view a 100m high tower 3Km away, find the height of the final image, when it is formed 25cm away from the eyepiece.

Suppose India had a target of producing by 2020 AD, 200000 MW of electric power, 10% of which was to be obtained from nuclear power plants. Suppose we are given that, on an average, the efficiency of utilisation (i.e.conversion to electric energy) of thermal energy produced in a reactor was 25%. How much amount of fissionable uranium would our country need per year by 2020? Take the heat energy per fission of \(^{ 235 }{ U }\) to be about 200 MeV.

Suppose a 'n'-type wafer is created by doping Si crystal having  \(5\times10^{ 28 }\)atoms/\({ m }^{ 3 }\)with 1 ppm concentration of As.On the surface 200 ppm Boron is added to create \('p'\)region in this wafer. Considering \({ n }_{ i }=1.5\times10^{ 16 }m^{ -3 }\) 
(i) Calculate the densities of the charge carriers in the   \(n\& p\) regions.
(ii) Comment which carriers would contribute largely for the reverse saturation current when diode is reverse biased.

A modulating signal is a square wave as shown in the figure.
The carrier wave is given by c(T) = 2 sin (8\(\pi \) t) volt.

(i) Sketch the amplitude modulated waveform
(ii) What is the modulation index?