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Compare the magnitudes of centripetal and centrifugal force.
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State two differences between the centripetal and centrifugal force.
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A boy experiences a centrifugal force on his hand when he rotates a piece of stone tied at one end of a string, holding the other end in the hand.
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Write the lens formula explaining the meaning of the symbols used.
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The correct lens formula is ______.
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- At what position a candle of length 3 cm be placed in front of a convex lens so that its image of length 6 cm be obtained on a screen placed at distance 30 cm behind the lens?
- What is the focal length of lens in part (a)?
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A concave lens forms the image of an object kept at a distance 20 cm in front of it, at a distance 10 cm on the side of the object.
- What is the nature of the image?
- Find the focal length of the lens.
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Where should an object be placed in front of a convex lens of focal length 0.12 m to obtain a real image of size three times the size of the object, on the screen?
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A lens forms the image of an object placed at a distance of 45 cm from it on a screen placed at a distance 90 cm on the other side of it. Find:
- the focal length of lens,
- the magnification of the image.
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What is an electric motor?
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Choose the correct relation for e.m.f. (ε) and terminal voltage V:
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A convex lens of focal length 10 cm is placed at a distance of 60 cm from a screen. How far from the lens should an object be placed so as to obtain a real image on the screen?
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We are able to see the T.V. channels clearly when we set T.V. on auto-tuning.
- Which phenomemon led to the clear visibility of the channels, due to auto-tuning?
- Define the above phenomenon mentioned by you.
- Give any one more example of this phenomenon.
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Find the value of current I drawn from the cell.

- Calculate the current I.
- Calculate the terminal voltage.
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The diagram below shows a cardboard on which iron filings are kept. A wire bent in the form of a loop is seen passing through the cardboard. When current flows through it, the iron filings arrange themselves as shown below.

- State the polarities of the battery at A and B.
- State the effect on the magnetic field if an iron rod is held along the axis of the coil.
- State one way to:
- Change the polarity of the coil.
- Decrease the strength of the magnetic field around the coil.
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The potential difference between terminals of a cell in a closed electric circuit is ______.
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State two factors affecting the coil's rotation speed in a D.C. motor.
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The image of a candle flame placed at a distance of 36 cm from a spherical lens, is formed on a screen placed at a distance of 72 cm from the lens. Calculate the focal length of the lens and its power.
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