Current Electricity Test

Result

Current Electricity Test - 4

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Question 1
4 / -1

Range of resistivity for metals is

A
10⁻⁶Ωm to 10⁻⁴Ωm

B
10⁻⁷Ωm to 10⁻⁵Ωm

C
10⁻⁸Ωm to 10⁻⁶Ωm

D
10⁻⁹Ωm to 10⁻⁷Ωm

Solution

The typical range of resistivity for metals is from 10⁻⁸Ωm to 10⁻⁶Ωm
Question 2
4 / -1

Wire wound resistors are made by

A
winding the wires of an alloy viz, Cu, Al, Ag

B
winding the wires of an alloy viz. Si, Tu, Fe

C
winding the wires of an alloy viz, Ge, Au, Gr

D
winding the wires of an alloy viz, manganin, constantan, nichrome

Solution

Wire bound resistors are made by winding the wires of an alloy, viz. manganin, constantan, nichrome etc. The choice of these materials is dictated mostly by the fact that their resistivities are relatively insensitive to temperature. These resistances are typically in range of a fraction of an ohm to a few hundred ohms.
Question 3
4 / -1

The resistivity of alloy manganin is

A
Nearly independent of temperature

B
Increases rapidly with increase in temperature

C
Decreases with increase in temperature

D
Increases rapidly with decrease in temperature

Solution

Metals, including alloys, have free electrons as charge carriers. Their movement controls by defects. One of defects of usual metal is oscillations of atoms due to temperature. More temperature - more oscillations - more collisions of electrons with atoms - less mobility - more resistivity. In alloys, like constantan, atoms are in disorder so alloys have big resistivity. Their additional disorder due to temperature increase is insignificant. That is why alloys have no temperature dependence of resistivity. The same picture is with metal glasses.
Question 4
4 / -1

Arrange the following materials in increasing order of their resistivity,
Nichrome, Copper, Germanium, Silicon

A
Copper < Nichrome < Germanium < Silicon

B
Germanium < Copper < Nichrome < Silicon

C
Nichrome < Copper < Germanium < Silicon

D
Nichrome < Germanium < Copper < Silicon

Solution
Question 5
4 / -1

What is the order of magnitude of the resistance of a dry human body?

A
10Ω

B
10kΩ

C
10MΩ

D
10μΩ

Solution

Human body has different resistances, when dry, resistance is 100,000 ohms. When wet because of sweat or water, resistance is only 1,000 ohms.