Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 3

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If $n, e, τ$ and $m$ are representing electron density, charge, relaxation time and mass of an electron respectively, then the resistance of a wire of length $I$ and cross-sectional area $A$ is given by

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Important Questions on Current Electricity

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 7

A potential difference of

5 V

is applied across a conductor of length

10 cm .

If drift velocity of electrons is

2.5 \times 10^{- 4} m s^{- 1},

then electron mobility will be

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 8

The resistance of a rectangular block of copper of dimensions

2 mm \times 2 mm \times 5 m

between two square faces is

0.02 Ω

. What is the resistivity of copper?

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 9

Two wires

A

and

B

of the same material, have radii in the ratio

1 : 2

and carry currents in the ratio

4 : 1

. The ratio of drift speed of electrons in

A

and

B

is

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 10

If a copper wire is stretched to make its radius decrease by

0.1 %,

then the percentage increase in resistance is nearly

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 11

A certain piece of copper is to be shaped into a conductor of minimum resistance. Its length and diameter should respectively be

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 12

A wire of resistance

x Ω

is drawn out, so that its length is increased to twice of its original length and its new resistance becomes

20 Ω

then,

x

will be

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 13

A piece of wire is cut into four equal parts and the pieces are bundled together side by side to form a thicker wire. Comparing the original wire, the resistance of the bundle is

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Gamma Question Bank for Medical Physics>Chapter 18 - Current Electricity>Assignment>Q 14

The temperature coefficient of resistance of a wire at

0 ° C

is

0.00125 ° C^{- 1} .

At

25 ° C

its resistance is

1 Ω .

. The resistance of the wire will be

1.2 Ω

at temperature