# Electrical Resistivity MCQ [Free PDF] – Objective Question Answer for Electrical Resistivity Quiz

1. Materials that easily allow the passage of electric current are known as ______

A. Insulators
B. Conductors
C. Dielectrics
D. Semi-conductors

Answer: B

Conductors are materials(mostly metals), which freely allow the passage of electrons through them. If electrons can flow freely through a material, it implies that even current can flow freely through that material since current is the rate of flow of electrons.

2. A wire of length 2m and another wire of length 5m are made up of the same material and have the same area of cross-section, which wire has higher resistance?

A. Both have equal resistance
B. The 2m wire has higher resistance
C. The 5m wire has higher resistance
D. The value of resistance cannot be determined from the given data

Answer: C

Resistance is directly proportional to the length of the wire, hence as the length of the wire increases, resistance increases.

3. A wire having an area of cross-section = 10sqm and another wire having an area of cross-section = 15sqm, have the same length and are made up of the same material. Which wire has more resistance?

A. Both have equal resistance
B. The 10sqm wire has higher resistance
C. The 15sqm wire has higher resistance
D. The value of resistance cannot be determined from the given data

Answer: B

Resistance is inversely proportional to the area of the cross-section. As an area of cross-section increases, resistance decreases. Hence the 10sqm wire has a higher resistance than the 15sqm wire.

4. Which of the following statements are true with regard to resistance?

A. Resistance is directly proportional to the length of the wire
B. Resistance is directly proportional to an area of a cross-section of the wire
C. Resistance is inversely proportional to the length of the wire
D. Resistance is inversely proportional to the resistivity of the wire

Answer: A

The expression for resistance is

Resistance = Resistivity × length of wire/ area of a cross-section of the wire.

Hence resistance is directly proportional to length.

5. A wire has the same resistance as the one given in the figure. Calculate its resistivity if the length of the wire is 10m and its area of the cross-section is 2m.

A. 16 ohm − meter
B. 8 ohm − meter
C. 16 kiloohm − meter
D. 8 kiloohm − meter

Answer: B

From the given circuit, R = V/I = 200/5 = 40ohm.

Resistivity = Resistance × Area of cross-section/ Length of the wire.

Resistivity = 40 × 2/10 = 8 ohm − metre.

6. Which, among the following is a unit for resistivity?

A. ohm/meter
B. ohm/meter2
C. ohm − meter
D. ohm − meter2

Answer: C

Resistivity = Resistance × Length/area of cross section.

Unit of resistivity = ohm × (m2)/m = ohm − m.

7. What is the resistivity of Copper?

A. 1.59 × 10 − 8ohm − m
B. 2.7 × 10 − 8ohm − m
C. 7.3 × 10 − 8ohm − m
D. 5.35 × 10 − 8ohm − m

Answer: A

Resistivity is a material property. Different materials have different resistivity. The resistivity of copper is 1.72 × 10 − 8 ohm − m.

8. Calculate the ratio of the resistivity of 2 wires having the same length and same resistance with an area of cross-section of 2m2 and 5m2 respectively.

A. 5:7
B. 2:7
C. 2:5
D. 7:5

Answer: C

Resistivity = R × A/L

Since the resistance and length of the two wires are the same so resistivity is directly proportional to the area of the cross-section. The ratio of the area is 2:5 so the ratio of resistivity is also 2:5.

9. Which of the following statements are true with regard to resistivity?

A. Resistance depends on the temperature
B. Resistance does not depend on the temperature
C. Resistivity depends on the length
D. Resistivity depends on the area of cross-section

Answer: A

Resistivity is a material property. It depends only on temperature.
For the same material with different lengths and areas, resistivity remains the same until the temperature remains constant.

10. The reciprocal of resistivity is________

A. Conductance
B. Resistance
C. Conductivity
D. Impedance

Answer: C

The expression for resistivity is = RA/l.

The expression for conductivity

= Cl/A; C = 1/R = > Conductivity = l/(AR) = 1/resistivity.

Hence, conductivity is the reciprocal of resistivity.

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