Single Choice

If a rod has resistance $$4\Omega$$ and if rod is turned as half circle, then the resistance along diameter is

A$$1.56\Omega$$
B$$2.44\Omega$$
C$$4\Omega$$
Correct Answer
D$$2\Omega$$

Solution

For rod, $$R = \rho \dfrac{l}{A}$$ .....................(1)

For half circle, length $$ = \pi r = l $$
Area = A
$$R = \rho \dfrac{\pi r}{A}$$
$$R = \rho \dfrac{l}{A}$$ ...................(2)

So, both the resistances are equal.

SIMILAR QUESTIONS

Current Electricity

A copper wire is stretched to make it $$0.5\%$$ longer. The percentage change in its electrical resistance if its volume remains unchanged is:

Current Electricity

A uniform wire of length $$l$$ and radius $$r$$ has a resistance of $$100\Omega$$. It is recast into a wire of radius $$\dfrac{r}{2}$$. The resistance of new 2 wire will be :

Current Electricity

When $$5V$$ potential difference is applied across a wire length $$0.1\ m$$, the drift speed of electron is 2.5 $$\times 10^{-4} ms^{-1}$$. If the electron density in the wire is 8 $$\times 10^{28} m^{-3}$$, the resistivity of the material is close to

Current Electricity

The resistance of a wire is $$R$$. It is bent at the middle by $$180^{\circ}$$ and both the ends are twisted together to make a shorter wire. The resistance of the new wire is

Current Electricity

The resistance of a 20 cm long wire is 5 $$\Omega$$. The wire is stretched to form a uniform wire of 40 cm length. The resistance now will be :

Current Electricity

If a copper wire is stretched to make its radius decrease by $$0.1$$%, then the percentage increase in its resistance is approximately:

Current Electricity

The resistance if a wire is '$$R$$' ohm. If it is melted and stretched to '$$n$$' times its original length, its new resistance will be:

Current Electricity

A wire of resistance $$4\:\Omega$$ is stretched to double its original length. The resistance of the stretched wire would be

Current Electricity

In an aluminum (Al) bar of square cross section, a square hole is drilled and is filled with iron (Fe) as shown in the figure. The electrical resistivities of Al and Fe are $$2.7 \times 10^{-8} \Omega$$ m and $$1.0 \times 10^{-7} \Omega$$ m, respectively. The electrical resistance between the two faces P and Q of the composite bar is

Current Electricity

If the length and area of cross-section of a conductor are doubled, then its resistance will be

Contact Details