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The effective resistance between A and B is:
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A cylindrical conductor of length l and uniform area of cross-section A has resistance R. Another conductor of length 2l and resistance R of the same material has an area of cross-section:
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Assertion: Conductors allow the current to flow through themselves.
Reason: They have free charge carriers.
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An induced emf is produced when a magnet is moved into a coil. The magnitude of induced emf does not depend on ____________.
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If two circular coils can be arranged in any of the three situations as shown in the diagrams below, then their mutual induction will be:
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The nature of magnetic field line passing through the centre of current carrying circular loop is ____________.
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Use the data in the Table given below to answer the following –
Which material is the best conductor?
Table give below Electrical resistivity of some substances at 20°C
| Electrical resistivity of some substances at 20°C | ||
| − | Material | Resistivity (Ω m) |
| Conductors |
Silver | 1.60 × 10−8 |
| Copper | 1.62 × 10−8 | |
| Aluminium | 2.63 × 10−8 | |
| Tungsten | 5.20 × 10−8 | |
| Nickel | 6.84 × 10−8 | |
| Iron | 10.0 × 10−8 | |
| Chromium | 12.9 × 10−8 | |
| Mercury | 94.0 × 10−8 | |
| Manganese | 1.84 × 10−6 | |
| Alloys |
Constantan (alloy of Cu and Ni) |
49 × 10−6 |
| Manganin (alloy of Cu, Mn and Ni) |
44 × 10−6 | |
| Nichrome (alloy of Ni, Cr, Mn and Fe) |
100 × 10−6 | |
| Insulators | Glass | 1010 − 1014 |
| Hard rubber | 1013 − 1016 | |
| Ebonite | 1015 − 1017 | |
| Diamond | 1012 − 1013 | |
| Paper (dry) | 1012 | |
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Carbon exists in the atmosphere in the form of ______.
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Structural formula of benzene is
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Vinegar is a solution of
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Which is the correct sequence of the components of a reflex arc?
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Which of the following statements are true?
- Sudden action in response to something in the environment is called reflex action
- Sensory neurons carry signals from spinal cord to muscles
- Motor neurons carry signals from receptors to spinal cord
- The path through which signals are transmitted from a receptor to a muscle or a gland is called reflex arc
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Junction between two neurons is called
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Label the parts (a), (b), (c) and (d) and show the direction of flow of electrical signals in the given figure.
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What are reflex actions? Give two examples. Explain a reflex arc.
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Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in Figure?
 |
 |
 |
 |
| Fig. A | Fig. B | Fig. C | Fig. D |
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Draw ray diagrams showing the image formation by a concave mirror when an object is placed
- between pole and focus of the mirror
- between focus and centre of curvature of the mirror
- at centre of curvature of the mirror
- a little beyond centre of curvature of the mirror
- at infinity
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How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?
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Meena draws magnetic field lines of field close to the axis of a current carrying circular loop. As she moves away from the centre of the circular loop she observes that the lines keep on diverging.
How will you explain her observation.
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Why does a magnetic compass needle pointing North and South in the absence of a nearby magnet get deflected when a bar magnet or a current carrying loop is brought near it. Describe some salient features of magnetic lines of field concept.
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