# MCQs on Electric Conduction, Ohm’s Law and Resistance ### Resistivity and Electrical Conductivity Question Bank:

Ques: The length of the resistance wire is increased by 10%. What is the corresponding change in the resistance of wire
(a) 10%
(b) 25%
(c) 21%
(d) 9%

Ans. (c)

Ques: All of the following statements are true except
(a) Conductance is the reciprocal of resistance and is measured in Siemens
(b) Ohm‘s law is not applicable at very low and very high temperatures
(c) Ohm‘s law is applicable to semiconductors
(d) Ohm‘s law is not applicable to electron tubes, discharge tubes and electrolytes

Ans. (c)

Ques: 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
(a) Current, electric field and drift speed
(b) Drift speed only
(c) Current and drift speed
(d) Current only

Ans. (d)

Ques: For which of the following the resistance decreases on increasing the temperature
(a) Copper
(b) Tungsten
(c) Germanium
(d) Aluminium

Ans. (c)

Ques: The electric resistance of a certain wire of iron is R. If its length and radius are both doubled, then
(a) The resistance will be doubled and the specific resistance will be halved
(b) The resistance will be halved and the specific resistance will remain unchanged
(c) The resistance will be halved and the specific resistance will be doubled
(d) The resistance and the specific resistance, will both remain unchanged

Ans. (b)

Ques: Conductivity increases in the order of
(a) Al, Ag, Cu
(b) Al, Cu, Ag
(c) Cu, Al, Ag
(d) Ag, Cu, Al

Ans. (b)

Ques: The relaxation time in conductors
(a) Increases with the increase of temperature
(b) Decreases with the increase of temperature
(c) It does not depend on temperature
(d) All of sudden changes at 400 K

Ans. (b)

Ques: A resistance R is stretched to four times its length. Its new resistance will be
(a) 4 R
(b) 64 R
(c) R/4
(d) 16 R

Ans. (d)

Related: Chemistry Chemical bonding Test

If an electric current is passed through a nerve of a man, then man
(a) Begins to laugh
(b) Begins to weep
(c) Is excited
(d) Becomes insensitive to pain

Ans. (c)

Ques: A steady current i is flowing through a conductor of uniform cross-section. Any segment of the conductor has
(a) Zero charge
(b) Only positive charge
(c) Only negative charge
(d) Charge proportional to current i

Ans. (a)

Ques: 5 amperes of current is passed through a metallic conductor. The charge flowing in one minute in coulombs will be
(a) 5
(b) 12
(c) 1/12
(d) 300

Ans. (d)

Related: Surface Chemistry MCQs

Ques: The conductivity of a superconductor is
(a) Infinite
(b) Very large
(c) Very small
(d) Zero

Ans. (a)

Ques: The resistance of an incandescent lamp is
(a) Greater when switched off
(b) Smaller when switched on
(c) Greater when switched on
(d) The same whether it is switched off or switched on

Ans. (c)

Ques: The resistance of a conductor increases with
(a) Increase in length
(b) Increase in temperature
(c) Decrease in cross–sectional area
(d) All of these

Ans. (d)

Ques: The specific resistance of all metals is most affected by
(a) Temperature
(b) Pressure
(c) Degree of illumination
(d) Applied magnetic field

Ans. (a)

Ques: A strip of copper and another of germanium are cooled from room temperature to 80 K. The resistance of
(a) Each of these increases
(b) Each of these decreases
(c) Copper strip increases and that of germanium decreases
(d) Copper strip decreases and that of germanium increases

Ans. (d)

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Ques: The temperature coefficient of resistance for a wire is 0.00125 / oC. At 300K its resistance is 1 ohm. The temperature at which the resistance becomes 2 ohm is
(a) 1154 K
(b) 1100 K
(c) 1400 K
(d) 1127 K

Ans. (d)

Ques: The resistance of a wire is R. If the length of the wire is doubled by stretching, then the new resistance will be
(a) 2R
(b) 4R
(c) R
(d) R/4

Ans. (b)

Ques: Ohm‘s law is true
(a) For metallic conductors at low temperature
(b) For metallic conductors at high temperature
(c) For electrolytes when current passes through them
(d) For diode when current flows

Ans. (a)

Ques: Which of the following is vector quantity
(a) Current density
(b) Current
(c) Wattless current
(d) Power

Ans. (a)

Ques: When there is an electric current through a conducting wire along its length, then an electric field must exist
(a) Outside the wire but normal to it
(b) Outside the wire but parallel to it
(c) Inside the wire but parallel to it
(d) Inside the wire but normal to it

Ans. (c)

Related: Questions on Electrostatics

Ques: The drift velocity does not depend upon
(a) Cross-section of the wire
(b) Length of the wire
(c) Number of free electrons
(d) Magnitude of the current

Ans. (b)

Ques: When a piece of aluminium wire of finite length is drawn through a series of dies to reduce its diameter to half its original value, its resistance will become
(a) Two times
(b) Four times
(c) Eight times
(d) Sixteen times

Ans. (d)

Ques: For a metallic wire, the ratio V / i (V = the applied potential difference, i = current flowing) is
(a) Independent of temperature
(b) Increases as the temperature rises
(c) Decreases as the temperature rises
(d) Increases or decreases as temperature rises, depending upon the metal

Ans. (b)

Ques: On increasing the temperature of a conductor, its resistance increases because
(a) Relaxation time decreases
(b) Mass of the electrons increases
(c) Electron density decreases
(d) None of the above

Ans. (a)