### Physics - Current Electricity

#### 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
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