Conductivity and Resistivity
Q. When 5 V potential difference is applied across a wire of length 10 cm, the drift speed of electrons is 2.5×10–4m/s. If the electron density in the wire is 8×1028/m3, then resistivity of the material is close to
Q. Iron-man needs a better suit to resist Thor’s lightning. What should he change to do this, given that he can’t change the dimensions (size and shape) of the suit.
- Change the material of the suit.
- Change the colour of the suit.
- Change the batteries of the suit.
- Change the name of the suit.
Q. For whatever reason, the relaxation time of a conductor increases by a factor of 2 and the number of electrons per unit volume decreases by a factor of 3. Given all other factors remain the same, the new conductivity changes by what factor?
The specific resistance of manganin is
50×10−8 Ω m.
The resistance of a manganin cube having length
50 cm is
- 10−6 Ω
- 2.5×10−5 Ω
- 10−8 Ω
- 5×10−4 Ω
Q. Following figure shows cross-sections through three long conductors of the same length and material, with square cross-section of edge lengths as shown. Conductor B will fit snugly within conductor A, and conductor C will fit snugly within conductor B. Relationship between their end to end resistance is
- Information is not sufficient
Q. What is the unit of conductivity and resistivity respectively?
- Ohm, mho
- Mho, ohm
- Ohm m, mho/m
- Mho/m, ohm m
Q. The conductivity of a material is 5 mho/m. What is it’s resistivity?
- None of these.
- 5 ohm m
- 0.2 ohm m
- 25 ohm m
Q. Masses of three wires are in the ratio 1 : 3 : 5 and their lengths are in the ratio 5 : 3 : 1. The ratio of their electrical resistance is
- 1 : 3 : 5
- 5 : 3 : 1
- 1 : 15 : 125
- 125 : 15 : 1
Q. Length of a hollow tube is 5m, it’s outer diameter is 10 cm and thickness of it’s wall is 5 mm. If resistivity of the material of the tube is 1.7×10−8 Ω m then the resistance of the tube will be
- None of these
- 5.6×10−5 Ω
- 2×10−5 Ω
- 4×10−5 Ω
Q. A material has a resistivity of 5 ohm m. The potential difference across the material was increased by a factor of 10. What is the new resistivity?
- 5 ohm m
- 50 ohm m
- 500 ohm m
- 0.5 ohm m