Physics - Current Electricity

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Question - 1

In order to have maximum current from a battery in an external wire of resistance R, the cells must be an external wire of resistance R, the cells must be arranged in such a combination so that the internal resistance r of the battery is

  • A r = R if cells are connected in series
  • B r = R if cells are connected in parallel
  • C r = R if cells are arranged in series-parallel combination
  • D r < R if cells are arranged in series-parallel combination

Question - 2

On dipping a conducting rod in boiling water, its conducitivity

  • A increases
  • B decreases
  • C remains unchanged
  • D decreased for thin rod but increases for thick rod

Question - 3

A conducting wire of lenght 'l' and radius of cross- section 'a' has resistance 4 ohms. It is melted to form a wire of length 4l.  Then resistance of new wire is

  • A 4 ohm
  • B 16 ohm
  • C 1 ohm
  • D 64 ohm

Question - 4

A uniform copper wire carries a current I ampere and has n carriers per \(metre^{3}\).  The length of the wire is l metre and its area of cross-section a \(metre^{2}\).  If the charge on a carrier is q coulombs, the drift velocity in \(ms^{-1}\) is given by

  • A \(naq\over l\)
  • B \(I\over naq\)
  • C \(Iln\over a\)
  • D \(I\over nalq\)

Question - 5

Tungsten wire obeys Ohm's law because

  • A the wire becomes hot when current flows
  • B the resistance is proportional to temperature
  • C the current is proportional to potential difference at constant temperature
  • D the current is proportional to the number of charge carriers

Question - 6

For making standard resistances such as 1.00 ohm, the material of the wire should best have a temperature coefficient of resistance which is

  • A low
  • B high
  • C negative
  • D zero

Question - 7

Electrical resistance can be

A. wire-bound resistance

B. carbon resistance

C. markedly with distance from the centre

D. decreases with distance from the centre

  • A A is correct
  • B A, B are correct
  • C A, C,D are correct
  • D A, B, C, D all are correct

Question - 8

In comparison to darbon resistances, the wattage of wire-wound resistance.  In general, are

  • A higher
  • B lower
  • C comparable
  • D negligibly small

Question - 9

Conductivity increases in the order of 

  • A silver, copper, aluminium, pure germanium
  • B pure germanium, aluminium, copper, silver
  • C pure germanium, copper, aluminium, silver
  • D copper, aluminium, silver, pure germanium

Question - 10

Instrument used to measure resistance is

  • A metre bridge
  • B voltmeter
  • C potentiometer
  • D electrometer