The specific resistance of all metals is most affected by :

1. Temperature

2. Pressure

3. Degree of illumination

4. Applied magnetic field

Subtopic:  Derivation of Ohm's Law |
 88%
From NCERT
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The positive temperature coefficient of resistance is for :

1. Carbon

2. Germanium

3. Copper

4. An electrolyte

Subtopic:  Current & Current Density |
 68%
From NCERT
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The electric intensity E, current density j and specific resistance k are related to each other by the relation :

1. E = j/k

2. E = jk

3. E = k/j

4. k = jE

Subtopic:  Current & Current Density |
 67%
From NCERT
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The resistance of a wire of uniform diameter d and length L is R. The resistance of another wire of the same material but diameter 2d and length 4L will be :

1. 2R

2. R

3. R/2

4. R/4

Subtopic:  Derivation of Ohm's Law |
 74%
From NCERT
PMT - 1984
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There is a current of 1.344 amp in a copper wire whose area of cross-section normal to the length of the wire is 1 mm2. If the number of free electrons per cm3 is 8.4 × 1022, then the drift velocity would be :

1. 1.0 mm/sec

2. 1.0 m/sec

3. 0.1 mm/sec

4. 0.01 mm/sec

Subtopic:  Current & Current Density |
 57%
From NCERT
PMT - 1990
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An electric wire of length ‘I’ and area of cross-section a has a resistance R ohms. Another wire of the same material having the same length and area of cross-section 4a has a resistance of :

1. 4R

2. R/4

3. R/16

4. 16R

Subtopic:  Derivation of Ohm's Law |
 75%
From NCERT
PMT - 1993
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If \(n\), \(e\), \(\tau\) and \(m\) respectively represent the density, charge relaxation time and mass of the electron, then the resistance of a wire of length \(l\) and area of cross-section \(A\) will be:
1. \(\frac{ml}{ne^2\tau A}\)
2. \(\frac{m\tau^2A}{ne^2l}\)
3. \(\frac{ne^2\tau A}{2ml}\)
4. \(\frac{ne^2 A}{2m\tau l}\)

Subtopic:  Current & Current Density |
 79%
From NCERT
PMT - 1992
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The relaxation time in conductors :

1. Increases with the increase in temperature

2. Decreases with the increase in temperature

3. It does not depend on the temperature

4. All of the sudden changes at 400 K

Subtopic:  Current & Current Density |
 73%
From NCERT
PMT - 2003
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Which of the following has a negative temperature coefficient of resistance?

1. C

2. Fe

3. Mn

4. Ag

Subtopic:  Derivation of Ohm's Law |
 71%
From NCERT
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The reciprocal of resistance is :

1. Conductance

2. Resistivity

3. Voltage

4. None of the above

Subtopic:  Derivation of Ohm's Law |
 84%
From NCERT
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