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Free Resistance and Resistivity MCQs with Answers

86 Resistance and Resistivity MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.

Resistance measures opposition to current in a conductor and follows R = V/I for an ohmic conductor, while resistivity is an intrinsic property of the material. Questions use R = ρL/A, examine effects of length, cross-sectional area and temperature, and distinguish resistance, resistivity, conductance and conductivity.

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86 questions · page 4 of 5

61. The length and radius of an electric resistance of a certain wire are doubled simultaneously, then the _.

  • A. Resistance will be doubled and specific resistance will be halved
  • B. Resistance will be halved and specific resistance will remain unchanged
  • C. Resistance will be halved and specific resistance will be doubled
  • D. Resistance and specific resistance will both remian unchanged

Explanation: Option B is correct since we know that, R = pl / A = pl / πr2 R' = p2l / / π(2r2) = R / 2 Specific resistance will remain the same as it…

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Correct answer: Resistance will be halved and specific resistance will remain unchanged

62. A 5 ohm resistor is indicated by a single _ colour band around its body.

  • A. Red
  • B. Green
  • C. Blue
  • D. Brown

Explanation: A carbon-composition resistor can have 4 to 6 bands. The assignment of colour according to their bands is shown in the table.The mnemonic…

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Correct answer: Green

63. The deviation of I-V graph from the straight line is due to:

  • A. Decrease in temperature and decrease in resistance
  • B. Increase in temperature and increase in resistance
  • C. Decrease in temperature and increase in resistance
  • D. Increase in temperature and decrease in resistance

Explanation: Explanation:The deviation of an I-V graph from a straight line is due to the fact that the resistance of a material changes with…

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Correct answer: Increase in temperature and increase in resistance

64. Three resistors each having value 'R' are connected as shown in the figure. What is the equivalent resistance between 'X' and 'Y'?

  • A. R
  • B. R/3
  • C. 3R
  • D. R3

Explanation: The resistors are connected in series so their equivalent resistance would be the sum of resistances of all resistors.R+R+R=3R.

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Correct answer: 3R

65. The resistance between two opposite faces of a square thin film of area 1 mm2 having a thickness of 1 m if the resistivity of the material is 10-6 Ω will be:

  • A. 1000 Ω
  • B. 100 Ω
  • C. 1 Ω
  • D. 10 Ω

Explanation: Given data Area, A= 1mm2 Resistivity, ρ= 10-6Ωm Thickness, x= 10-6m Now we have Resistance, R=ρl/A where A= = length (l) x thickness (x)…

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Correct answer: 1 Ω

66. Total resistance between 'A' and 'B' in the given circuit is:

  • A. 5.6 Ω
  • B. 3.33 Ω
  • C. 0.33 Ω
  • D. 6.6 Ω

Explanation: The total resistance can be found by using the method of successive reduction, as shown below

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Correct answer: 6.6 Ω

67. A carbon resistor connected to a battery of 50V and 2A current is passing through it. If voltage is increased to 75V then current will be:

  • A. 1.5A
  • B. 3A
  • C. 4.5A
  • D. 6A

Explanation: Firstly, we'll calculate the resistance of the carbon resistor by using the formula Voltage= Current x Resistance.

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Correct answer: 3A

68. The effective resistance between the points A and B in the figure is

  • A. 2 Ohms
  • B. 6 Ohms
  • C. 3 Ohms
  • D. 4 Ohms

Explanation: Resistor AD and DC are in series For series combination: Re=R1+R2 =AD+DC =3ohm+3ohm =6ohm, this is in parallel combination with resistor…

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Correct answer: 2 Ohms

69. The unit of conductance is

  • A. Ohm
  • B. Ohm-meter-1
  • C. Ohm - meter
  • D. mho

Explanation: The SI unit for conductance is siemen or mho. This is also written as 1/ohm or ohm-1.

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Correct answer: mho

70. The resistance of the three arms of the balanced wheat stone bridge is 50 ohms. The resistance in the 4 ohm range is:

  • A. 25 ohm
  • B. 50 ohm
  • C. 75 ohm
  • D. 100 ohm

Explanation: In a balanced Wheatstone bridge, the ratio of the resistances in one arm is equal to the ratio of the resistances in the other arm…

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Correct answer: 50 ohm

71. Ohm's law is valid only for currents following in:

  • A. Metallic conductor
  • B. Transistors
  • C. Diodes
  • D. Electric arcs

Explanation: Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points…

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Correct answer: Metallic conductor

72. A 50Ω resistance wire is stretched such that its length is doubled and its cross section area becomes half. The new resistance is:

  • A. 100Ω
  • B. 200Ω
  • C. 50Ω
  • D. 150Ω

Explanation: The resistance R of a wire is given by the formula: R = ρL/A, where ρ is the resistivity, L is the length, and A is the cross-sectional…

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Correct answer: 200Ω

73. An efficient voltmeter has:

  • A. Low resistance in comparison to circuit resistance
  • B. High resistance in comparison to circuit resistance
  • C. A resistance equal to circuit resistance
  • D. None of the above

Explanation: High resistance in comparison to circuit resistance: This is the correct option.

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Correct answer: High resistance in comparison to circuit resistance

74. The two metals having the same resistance can be differentiated by their value:

  • A. Resistance
  • B. Conductance
  • C. Temperature coefficient of resistivity
  • D. Conductivity

Explanation: When two metals have the same resistance, they can be differentiated based on their conductivity.

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Correct answer: Conductivity

75. A wir of uniform cross section A, length I and resistance R is cut into two equal pieces. The resistivity of each piece will be

  • A. the same
  • B. one fourth
  • C. double
  • D. one half

Explanation: Resistivity remains constant, it is a constant value.

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Correct answer: the same

76. Three equivalent resistors connected in parallel have equivalent resistance R/3. When they are connected in series then the equivalent resistance is:

  • A. 3R
  • B. R/3
  • C. R
  • D. 2R

Explanation: When three equivalent resistors are connected in parallel, the equivalent resistance is 3/R.

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Correct answer: 3R

77. Which of the following are Ohmic materials?

  • A. Semiconductors
  • B. Tungsten filament
  • C. Thermistor
  • D. Metals

Explanation: Ohmic materials are those that follow Ohm's Law, where the resistance (R) is constant regardless of the applied voltage (V) or current…

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Correct answer: Metals

78. A wire has a resistance 'R'. If its length is doubled and radius is reduced to half then its resistance will become:

  • A. 2R
  • B. 4R
  • C. 8R
  • D. 16R

Explanation: To determine the new resistance, use the formula Resistance = resistivity × length/area.

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Correct answer: 8R

79. Which one of the following has negative temperature coefficient?

  • A. Copper
  • B. Thermistor
  • C. Soft iron
  • D. Platinum

Explanation: NTC, negative thermistors are resistors with a negative temperature coefficient which means the resistance decreases with increasing…

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Correct answer: Thermistor

80. A generator produces 100 kW of power at a potential difference of 10KV. The power is transmitted through cables of total resistance 5Q. How much power is dissipated in the cables?

  • A. 50 W
  • B. 750 W
  • C. 500 W
  • D. 1000 W

Explanation: To find the power dissipated in the cables, you need to first calculate the current flowing through the circuit.

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Correct answer: 500 W
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