Mandeep's mother had put lot of clothes for washing in the washing machine, but the machine did not start and an indicator was showing that the lid of the machine did not close. Mandeep seeing his mother disturbed thought that, he would close the lid by applying some force but would close the lid by applying some force but realised that the mechanism was different. It was a magnetic system. He went to the shop and got a small magnetic door closer and put it on the lid of the machine. The machine started working. His mother was happy that Mandeep helped her to save 500 rs also.
i) What were the values developed by Mandeep?
ii) What values did his mother impart to Mandeep?
iii) Every magnetic configuration has a North pole and a South pole, What about the field due to toroid?

A magnetic dipole is placed in a uniform magnetic field with its axis tilted with respect to its position of stable equilibrium. Deduce an expression for the time period of (small amplitude) oscillation of this magnetic dipole about an axis, passing through its centre and perpendicular to its plane. If this bar magnet is replaced by a combination of two similar bar magnets, placed over each other, how will the time period vary?

A group of students while coming from the school noticed a box marked "Danger HT 2200 V" at a substation in the main street. They did not understand the utility of a such high voltage, while they argued, the supply was only 220 V. They asked their teacher this question the next day. The teacher thought it to be an important question and therefore explained to the whole class.
Answer the following questions:
(i) What device is used to bring the high voltage down to low voltage of AC current and what is the principle of its working?
(ii) Is it possible to use this device for bringing down the high DC voltage to the low voltage? Explain.
(iii) Write the values displayed by the students and the teacher.

A resistor of \(400\Omega \) an inductor of \(\frac { 5 }{ \pi H } \)and a capacitor of \(\frac { 50 }{ \pi } \mu F\) are connected in series across a source of alternating voltage of 140 \(sin\ \pi t\ V\). Find the voltage (rms) across the resistor, the inductor and the capacitor. Is the algebraic sum of these voltage more than the source voltage? If yes, resolve the paradox.

The critical angle between a given transparent medium and air is denoted by C. A ray of light in air enters this transparent medium at an angle of incidence equal to polarizing angle p. Deduce a relation for the angle of refraction in terms of C.

A teacher has given three lenses of power 0.5D, 4D and 10D to a studet. He is not sure as to which lens should he use for constructing a good astronomical telescope. So, he consults his seniors and the teacher, and then constructs a telescope. Later, he shows this telescope to the junior classes and ex[plains about the choice of lenses.
Read the above passage and give the answer of the following questions:
(i) What values has he shown by doing these?
(ii) Which lenses are used as objective and which one as eyepiece?

(i) In a double slit experiment using light of wavelength 600 nm, the angular width of the fringe formed on a distant screen is \(0.1^o\) . Find the spacing between the two slits.
(ii) Light of wavelength 5000\(\dot { A } \) propagating in air gets partly reflected from the surface of water. How will the wavelengths and frequencies of the reflected and refracted light be affected?