The resistance of a discharge tube is :

(1) Ohmic

(2) Non-ohmic

(3) Both (1) and (2)

(4) Zero

Concept Questions :-

Derivation of Ohm's law
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A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/ quantities constant along the length of the conductor is/are :

(1) Current, electric field and drift speed

(2) Drift speed only

(3) Current and drift speed

(4) Current only

Concept Questions :-

Current and current density
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σ1 and σ2 are the electrical conductivities of Ge and Na respectively. If these substances are heated, then

(1) Both σ1 and σ2 increase

(2) σ1 increases and σ2 decreases

(3) σ1 decreases and σ2 increases

(4) Both σ1 and σ2 decrease

Concept Questions :-

Derivation of Ohm's law
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In the figure a carbon resistor has bands of different colours on its body as mentioned in the figure. The value of the resistance is 

(1) 2.2 kΩ

(2) 3.3 k kΩ

(3) 5.6 k kΩ

(4) 9.1 kΩ

Concept Questions :-

Colour coding of resistors
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Masses of 3 wires of same metal are in the ratio 1 : 2 : 3 and their lengths are in the ratio 3 : 2 : 1. The electrical resistances are in ratio

(1) 1 : 4 : 9

(2) 9 : 4 : 1

(3) 1 : 2 : 3

(4) 27 : 6 : 1

Concept Questions :-

Derivation of Ohm's law
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A wire of radius r has resistance R. If it is stretched to a radius of 3r4, its resistance becomes 

(1) 9R16

(2) 16R9

(3) 81R256

(4) 256R81

Concept Questions :-

Derivation of Ohm's law
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A copper wire has a square cross-section, 2.0 mm on a side. It carries a current of 8 A and the density of free electrons is 8 × 1028 m–3. The drift speed of electrons is equal to 

(1) 0.156 × 10–3 m.s–1

(2) 0.156 × 10–2 m.s–1

(3) 3.12 × 10–3 m.s–1

(4) 3.12 × 10–2 m.s–1

Concept Questions :-

Current and current density
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What length of the wire of specific resistance 48×108Ω  mis needed to make the resistance of 4.2 Ω (diameter of wire = 0.4 mm

(1) 4.1 m

(2) 3.1 m

(3) 2.1 m

(4) 1.1 m

Concept Questions :-

Derivation of Ohm's law
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A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of 

(1) Each of these increases

(2) Each of these decreases

(3) Copper strip increases and that of germanium decreases

(4) Copper strip decreases and that of germanium increases

Concept Questions :-

Derivation of Ohm's law
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The length of a given cylindrical wire is increased by 100%. Due to the consequent decrease in diameter, the change in the resistance of the wire will be :

(1) 300%

(2) 200%

(3) 100%

(4) 50%

Concept Questions :-

Derivation of Ohm's law
To view Explanation, Please buy any of the course from below.
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level: