Answer the questions.[Phy-3M]

Question 13 Marks

a. Draw the pattern of magnetic field lines produced by a current carrying circular loop showing the direction of current in the loop and the direction of the magnetic field lines.
b. State the rule which can be applied to know the direction of magnetic field lines in the above case.

Answer

b. Right Hand Thumb Rule:- When a current carrying straight conductor is held in the right hand in such a way that the thumb points towards the direction of the current, then the fingers will wrap around the conductor in the direction of the field lines of the magnetic field

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Question 23 Marks

Find out the following in the electric circuit given in Figure

i. The effective resistance of two $8 \Omega$ resistors in the combination
ii. Current flowing through $4 \Omega$ resistor

Answer

Given :-
Resistor, $\mathrm{R}_{1}=4 \Omega$
Resistor, $\mathrm{R}_{2}=8 \Omega$
Resistor, $\mathrm{R}_{3}=8 \Omega$
Potential Difference, $\mathrm{V}=8$ volts.
i. Since two $8 \Omega$ resistances are in parallel, their effective resistance (Rp) is given by $\frac{1}{R^{\prime}}=\frac{1}{8}+\frac{1}{8}+\frac{1}{4}$ or $\mathrm{R}^{\prime}=4 \Omega$
ii. The total resistance in the circuit, $R=4 \Omega+R_{p}=4 \Omega+4 \Omega=8 \Omega$
Current through the electric circuit, $I=\frac{V}{R}=\frac{8}{4}=2 A$
Since $4 \Omega$ resistor and Rp are in series, the current through $4 \Omega$ resistors $=1 \mathrm{~A}$.

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Question 33 Marks

1. Write the function of each of the following parts of human eye : cornea, iris, crystalline lens, ciliary muscles.
2. Millions of people of the developing countries of world are suffering from corneal blindness. These people can be cured by replacing the defective cornea with the cornea of a donated eye.
A charitable society of your city has organised a campaign in your neighbourhood in order to create awareness about this fact.
If you are asked to participate in this mission how would you contribute in this noble cause?
1. State the objective of organising such campaigns.
2. List two arguments which you would give to motivate the people to donate their eyes after death.
3. List two values which are developed in the persons who actively participate and contribute in such programme.

Answer

1. Functions of following parts of human eye are given below :
1. Cornea - It is a thin membrane which provides $67 \%$ of the eye's focussing power.
2. Iris - It controls amount of light entering the eye by controlling the size of pupil similar to the aperture of a camera which has capacity to decrease or increase the amount of light entering eye.
3. Crystalline lens - It helps to focus light on retina for image formation.
4. Ciliary muscles - It contracts and relax in order to change the lens shape for focussing image at retina. when it contracts the lens become thicker and when it relaxes the lens become flat.
2. 1. The objective of organising such compaigns is to guide, educate and help those people who are suffering from corneal blindness that they can be cured by corneal replacement surgery.
2. 1. Come to participate in this campaign because, if someone get his vision through your eyes, it is an incredible help.
2. As eye is one of the most valuable sense organs through which an individual can achieve so many things in his/her life, so try to realise the situation that these people are suffering from.
3. The persons who actively participate and contribute in such programme are strong hearted and very much helpful for the people living in such situations.

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Science Answer the questions.[Phy-3M]

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