# Conductivity and Resistivity

## Trending Questions

**Q.**For two resistor R1 and R2 connected in parallel the relative error in their equivalent resistance is {where R1 = (10.0 +- 0.1) and R2 = (20.0 +- 0.4)} a) 0.08 b) 0.05 c) 0.01 d) 0.04

**Q.**

The resistances in the two arms of the meter bridge are 5Ω and RΩ, respectively. When the resistance R is shunted with an equal resistance, the new balance point is at 1.6, the resistance R is

10Ω

20Ω

25Ω

15Ω

**Q.**

How can three resistors of resistances $2\Omega ,3\Omega $ and $6\Omega $ be connected to give a total resistance of $1\Omega $?

**Q.**

What is Cell Constant?

**Q.**

A silver wire has a resistance of 2.1 Ω at 27.5 °C, and a resistance of 2.7 Ω at 100 °C. Determine the temperature coefficient of resistivity of silver.

**Q.**An electron is projected with uniform velocity along the axis of a current carrying long solenoid. Which of the following is true?

- The electron will experience a force at 45∘ to the axis and hence execute a helical path.
- The electron path will be circular about the axis.
- The electron will continue to move with uniform velocity along the axis of the solenoid
- The electron will be accelerated along the axis.

**Q.**The equivalent resistance between points A and B with switch S open and closed are respectively:

- 4Ω, 8Ω
- 8Ω, 4Ω
- 6Ω, 9Ω
- 9Ω, 6Ω

**Q.**

Two capacitors with capacitance values ${\mathrm{C}}_{1}=2000\pm 10\mathrm{pF}$ and ${\mathrm{C}}_{2}=3000\pm 15\mathrm{pF}$ are connected in series. The voltage applied across this combination is 𝑉 = 5.00 ± 0.02 V. The percentage error in the calculation of the energy stored in this combination of capacitors is _______.

**Q.**

Two identical metal wires of thermal conductivities ${K}_{1}$ and ${K}_{2}$ respectively are connected in series. The effective thermal conductivity of the combination is:

$\frac{2{K}_{1}{K}_{2}}{{K}_{1}+{K}_{2}}$

$\frac{{K}_{1}+{K}_{2}}{{K}_{1}{K}_{2}}$

$\frac{{K}_{1}+{K}_{2}}{2{K}_{1}{K}_{2}}$

$\frac{{K}_{1}{K}_{2}}{{K}_{1}+{K}_{2}}$

**Q.**

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.**If the resistance of a conductor is 5 Ω at 50∘C and 7 Ω at 100∘C, then the mean temperature coefficient of resistance is

- 0.06(∘C)−1
- 0.08(∘C)−1
- 0.01(∘C)−1
- 0.04(∘C)−1

**Q.**For a series RLC circuit R=XL=2XC. The impedance of the circuit and phase difference (between) V and i will be

- √5R2, tan−1(2)
- √5R, tan−1(12)
- √5R2, tan−1(12)
- √5XC, tan−1(2)

**Q.**Two wires of same dimensions but different resistivities ρ1 and ρ2 are connected in series. The equivalent resistivity of the combination is

- ρ1+ρ22
- √ρ1ρ2
- ρ1+ρ2
- None of the above

**Q.**

Unit of electric susceptibility?

**Q.**In a conductor, if the number of conduction electrons per unit volume is 8.5×1028 m3 and mean free time is 25 fs (femto second), it's approximate resistivity is :

(me=9.1×10−31 kg)

- 10−8 Ω m
- 10−7 Ω m
- 10−5 Ω m
- 10−6 Ω m

**Q.**

The resistivity of the metallic conductor is given by the relation

**Q.**

A cylindrical conductor of length $\u2018l\u2019$ and uniform area of cross-section $\u2018A\u2019$ has resistance $\u2018R\u2019$. The area of cross-section of another conductor of the same material and same resistance but of length $\u20182l\u2019$ is

$\frac{A}{2}$

$\frac{3A}{2}$

$2A$

$3A$

**Q.**If length of a wire increases by 0.1% due to stretching, the percentage increase in its resistance will be (Assume cross sectional area as constant)

- 1%
- 0.2%
- 2%
- 0.1%

**Q.**

which of the following has low resistivity

copper

silver

manganin

constantan

**Q.**

How does dielectric affect energy stored?

**Q.**

Does the energy stored in a capacitor increase when the dielectric is removed?

**Q.**A carbon resistor has following colour code. What is the value of the resistance ?

- 6.4 MΩ±5%
- 64 MΩ±10%
- 530 kΩ±5%
- 5.3 kΩ±5%

**Q.**

Two conducting wires of the same material and of equal lengths and equal diameters are first connected in series and then parallel in a circuit across the same potential difference. What is the ratio of heat produced in series and parallel combinations?

**Q.**

State the conditions under which Ohms law is not obeyed in a conductor.

**Q.**

What cause of resistance in a conductor?

**Q.**

What do you mean by the dynamic resistance of a conductor?

**Q.**A solid spherical conductor of radius R has a spherical cavity of radius a(a

**Q.**Two conductors having same width and length, thickness d1 and d2, thermal conductivity K1 and K2 are placed one above the another. Find the equivalent thermal conductivity parallel to the contact surface such that the temperature difference across both the faces of both the conductors are same.

- (d1 + d2)(K1d2 + K2d2)2(K1 + K2)
- (d1−d2)(K1d2 + K2d2)2(K1 + K2)
- K1d1 + K2d2d1 + d2
- K1 + K2d1 + d2

**Q.**

The resistance of a wire is r ohms. It is stretched to double its length. The new resistance of the wire in ohms is

r/2

r/4

2r

4r

**Q.**A rod of certain metal is 1 m long and 0.6 cm in diameter. It’s resistance is 3×10−3 Ω. A disc of the same metal is 1 mm thick and 2 cm in diameter, what is the resistance between it’s circular faces.

- 1.35×10−6 Ω
- 2.7×10−7 Ω
- 4.05×10−6 Ω
- 8.1×10−6 Ω